The sources for Bauch's death are the registration card (which can be found online at
www.fold3.com), Bundsearchiv RL 2-III/1044 (which lists one JGr. 200 pilot dead on 25 June 1944) and RL 2-III/823 (one JGr. 200 pilot killed by enemy action on an operational flight on 25 June).
From the UK National Archives, ULTRA decrypt CX/MSS/R.235(C),11 says:
Report No. 954 of 2/7, from Jafü SOUTH, IA:
Ref: Jafü SOUTH IA’s No. 940 of 25/6.
Subject: Supplement to monthly report of Jafü SOUTH FRANCE for June (25–30/6).
Operated on scrambles: 59 a/c, victories 2 4-engined a/c shot out of formation: 3 4-engined a/c and 3 S.E. a/c effectively shot up.
Losses: 1 Me 109 shot down, pilot killed. 1 Me 109 made forced landing, pilot injured (battle losses over our own territory).
As far as I remember, I got my American claims information from the late Frank Olynyk's lists and the the mission reports the 82nd FG website (which is no longer live). For the 31st FG, I probalby used
https://www.wwiiaircraftperformance....t-reports.html
We can only guess how Bauch was given his victory credit but it is not impossible that another pilot witnessed the event and reported it. We obviously don't know if Bauch was able to call it in on the radio during the action.
P.S. Klauka's death is recorded by the above BA sources and his registration card as accidental, at 18.00 hrs. on 28 June at Aix-les-Milles. The BA sources also record one pilot wounded in action on the 29th (which I take to be Bernhardt) but CX/MSS/T230/16 says "… Fourthly, day 29th: … (D) Jafü South total effort 18 Me 109 sorties in 6 ops. No claims or losses."