Bartels four P-38 claims on 15.11.43 were imo true. Now as to what happened to those P-38's. On 15.11.43 it was a very heavy overcast, so Bartels would not have likely seen what happened to the P-38s after he shot them up and they went down through the heavy overcast. Mitchells pilots reported four P-38s got 'holed'. One went down and crashed near Kalamaki (found), apparently the other 3 all made it back to their home base in Foggia, Italy, but, all three crashed when they landed do to Hydraulic / Brake / Control surfaces problems. It dosn't say if those P-38s were repaired or replaced. So I would call all of those kills. Other people may not.
What is your source for the crash landing/battle damage data? Absent the official Battle Damage or Accident reports as well as the Mission Summary there would be no fact based derivative for cause/effect?
Second, the LW did not count a shot up/crash landed 109 as a 'loss' because it was not salvaged. Why would you count a returned P-38 w/Battle damage as a 'loss" if it also was not written off?
Have you thought that you may be biased to Bartels and trying to explain discrepancies in his credits without all the facts in hand?
As 'to not seeing what happened" - in the USAAF most of those were awarded 'Damaged" or "Probable" versus "Destroyed". They made mistakes as all Air Forces did. But the official criteria for credit evaluation as Destroyed were a.) seen to blow up, b.) lost a major structural component rendering the a/c unflyable, c.) seen to crash, d.) pilot/crew seen to bail out, e.) seen to be on fire and/or out of control.
The last criteria was usually subjective and resulted in most variances of claim to credit. LW pilots were known to put an Fw 190 into a spin - which was recoverable more often than a Mustang or Me 109.
This is a list of all MACR's for USAAF 15 November 1943. Looks like (1) P-38 from the 1st FG failed to return, for which a Macr 1306 was created
431115 B-24 42-7617 6AF CARIBBEAN 1091
431115 F-5 42-13275 5 ADRIATIC 1121
431115 P-40 42-105509 8 NEW GUINEA 1191
431115 P-47 42-8413 355 FRANCE 1289
431115 P-47 42-8408 155 FRANCE 1290
431115 P-38 43-2184 1 GREECE 1306
431115 B-24 42-40409 308 CHINA 12394