To track a loss in 1944, you can check two sources:
1) Flugzeugbestand und Bewegungsmeldungen, available for most units on
http://www.ww2.dk/air.html.
This show that for your period (June to September 1944) the only JG 5 unit that had Fw 190s was IV./JG 5
The following "losses" were listed for this Gruppe:
June: 1 Fw 190 A-3 to "Überholung" (overhaul)
July: no FW 190 lost
August: 2 Fw 190 A-3 to "Überholung"
September: 4 Fw 190 F-8 and 1 Fw 190 A-8 to enemy action, 2 Fw 190 A-3, 1 Fw 190 A-8 and 1 Fw 190 F-8 without enemy action
So from this source, it seems that September 1944 could be the right month. AFAIK this documents lost all aircraft lost to the unit, meaning aircraft effectively destroyed, missing or damaged beyond repair, but also those repairable outside the unit and so transferred to a repair facility.
Of the 9 Fw 190 losses above, only two were in my list above, because pilots were killed.
2) the database of the Luftwaffe losses summary, available for some units (but AFAIK all JG units) at
http://www.ahs.no/ref_db/lw_summ_los...iew.asp?PAGE=1
For IV./JG 5 in September 1944 there is:
05/09/1944 1 Destroyed without enemy action on non-operational flight
07/09/1944 1 Destroyed without enemy action on non-operational flight
10/09/1944 1 Damaged without enemy action on non-operational flight
17/09/1944 1 Damaged without enemy action on non-operational flight
19/09/1944 1 Destroyed without enemy action on non-operational flight
22/09/1944 1 Damaged without enemy action on non-operational flight
25/09/1944 1 Destroyed by gunfire from enemy aircraft during operational flight, observed by enemy
25/09/1944 1 Damaged by gunfire from enemy aircraft during operational flight, not observed by enemy
26/09/1944 3 Destroyed by gunfire from enemy aircraft during operational flight, observed by enemy
26/09/1944 1 Damaged without enemy action on operational flight
27/09/1944 1 Damaged without enemy action on non-operational flight
29/09/1944 1 Damaged without enemy action on operational flight
29/09/1944 1 Destroyed by gunfire from enemy aircraft during operational flight, observed by enemy
Total: 15 losses
Destroyed by gunfire from enemy aircraft during operational flight, observed by enemy: 5
Damaged by gunfire from enemy aircraft during operational flight, not observed by enemy: 1
Damaged without enemy action on operational flight: 2
Destroyed without enemy action on non-operational flight: 3
Damaged without enemy action on non-operational flight: 4
As said above, IV./JG 5 Bewegungsmeldungen reported 9 Fw 190 lost in September 1944, but also 6 Bf 109s (1 to enemy action, 5 without), so both sources are coherent (that is not always the case)
Compare it with the loss list from the old luftwaffe.no loss list:
Date;Aircraft;Unit;Start;S.det.;WNr;Vknz.;Reason;; Dam.;Loss;Pilot;Ploss;Area;Place down
05/09/1944;Messerschmitt Bf 109 G;IV./JG 5;Petsamo;5F;;;Accident;;;?%;Pilot unk;unk;FINLAND;Par/ ved Petsamo flyplass?
07/09/1944;Messerschmitt Bf 109 G;IV./JG 5;Petsamo;5F;;;Accident;betjening;;?%;Pilot unk;unk;FINLAND;Sta/ eller Lan/ Petsamo flyplass
10/09/1944;Messerschmitt Bf 109 G;IV./JG 5;Salmijärvi;5F;;;Accident;betjening;?%;;Pilot unk;unk;FINLAND;Nla/ Salmijärvi omr.
17/09/1944;Messerschmitt Bf 109 G;IV./JG 5;Salmijärvi;5F;;;Accident;betjening;?%;;Pilot unk;0-0-0-1;FINLAND;Nla/ Salmijärvi omr.
19/09/1944;Messerschmitt Bf 109 G;IV./JG 5;Nautsi?;5F;;;Accident;betjening;;100%;Pilot unk;unk;FINLAND;Cra/ Nautsi området
26/09/1944;Focke-Wulf Fw 190 F-8;13./JG 5;unk;?A;WNr. 058 1665;Weisse 11;Russian A/C;;;100%;Uffz. Kurt Thonemann (+);1-0-0-0;NORWAY;Cra/s off Vadsø
26/09/1944;Focke-Wulf Fw 190 F-8;13./JG 5;unk;5F;WNr. 581668;Hvit 10;Russian A/C;;;100%;Uffz. Hermann Hagenmeyer (+);1-0-0-0;NORWAY;Cra/s Vadsø omr.
That gives:
05/09/1944: 1 Bf 109 destroyed without enemy action on non-operational flight, possibly in Petsamo area
07/09/1944: 1 Bf 109 destroyed without enemy action on non-operational flight, on landing at Petsamo
10/09/1944: 1 Bf 109 damaged without enemy action on non-operational flight, force-landed in Salmijärvi area
17/09/1944: 1 Bf 109 damaged without enemy action on non-operational flight, force-landed in Salmijärvi area
19/09/1944: 1 Bf 109 destroyed without enemy action on non-operational flight, crashed in Nautsi area
(at this point we have already five Bf 109 losses without enemy action, so all losses without enemy action below should be Fw 190s)
22/09/1944: 1 Fw 190 damaged without enemy action on non-operational flight
25/09/1944: 1 Bf 109 or Fw 190 destroyed by gunfire from enemy aircraft during operational flight, observed by enemy
25/09/1944: 1 Bf 109 or Fw 190 damaged by gunfire from enemy aircraft during operational flight, not observed by enemy
26/09/1944: 2 Fw 190s (identified) and one Bf 109 or Fw 190 destroyed by gunfire from enemy aircraft during operational flight, observed by enemy
26/09/1944: 1 Fw 190 damaged without enemy action on operational flight
27/09/1944: 1 Fw 190 damaged without enemy action on non-operational flight
29/09/1944: 1 Fw 190 damaged without enemy action on operational flight
29/09/1944: 1 Bf 109 or Fw 190 destroyed by gunfire from enemy aircraft during operational flight, observed by enemy
Conclusion: no Fw 190 of IV./JG 5 destroyed in a crash in west Norway between June and September 1944 according to these sources
Second conclusion: the old luftwaffe.no loss list possibly puts Bf 109s for the losses above (for which most details are lacking) as the main aircraft of the Gruppe. If this is the case, there is a possibility that one of the total losses of the 5th, 7th and 19th might be a Fw 190. Losses at the start of the month, especially the first with a question mark on location could be during the move north from SW Norway to the northern front.