Confusion indeed. However, 42-24638 may not have been lost at all, hence no MACR. It appears twice in the latter half of 1945 on the AAIR and Accident-report.com websites as having had accidents at Maxwell Field, Alabama with 2132 AAF Base Unit.
Likely turned into a TB-29 for training purposes with armaments removed, given its post-war station.
There's a picture here:
https://upload.wikimedia.org/wikiped...ell.750pix.jpg
To be absolutely sure, one has to request the accident forms or the Individual Aircraft Record Card for #638.
I assume MACR 10644 is correct re serial.
Also note that 24-24687 (500th BG) had ditched with all crew lost (MACR 10659) as was 42-63430 of 498th BG (MACR 10655).
Regards,
Leendert