According to my references the 51st Bomb Squadron of/and the 46th Bomb Group (L) NEVER LEFT THE USA during the war:
46th Bombardment Group
Constituted as 46th Bombardment Group (Light) on 20 Nov 1940. Activated on 15 Jan 1941. Trained with A-20's.Flew some antisubmarine patrols over the Gulf of Mexico early in 1942. Assigned to Second AF in August and to Third AF in Nov 1942. Served as an operational training unit until late in 1943, then became a replacement training unit. Disbanded on 1 May 1944.
Stations: Savannah, Ga, 15 Jan 1941; Bowman Field, Ky, 20 May 1941; Barksdale Field, La, Feb 1942; Galveston Mun Aprt, Tex, c. 1 Apr 1942; Blythe AAB, Calif, 23 May 1942; Will Rogers Field, Okla, Nov 1942; Drew Field, Fla, Oct 1943; Morris Field, NC, 6 Nov 1943-1 May 1944. Disbanded on 1 May 1944.
Now we have a historical disconnect and have to figure out how/why your uncle got to North Africa--NOT with the 51BS/46BG.
According some resoucres I checked only three aircraft were reported missing as a result of combat on 8MAR43.These were from the 305th, 306th and 44th Bomb Groups.Respectively they were 2 B-17s and a B-24.
3/8/1943 B-24 41-23988 44BG67BS "Emmy Lou"--apparently one of two losses on 8th AF mission to Rouen
3/8/1943 B-17 41-24588 305 364BS 41-24588 shot down Feb 1943 over English Channel.All crew KIA.
3/8/1943 B-17 41-24514 306BG 368BS 41-24514 (306th BG) lost 3/8/1943, France.
Now I checked dates on both sides of March 8 and noted that all combat flying in the MTO was cancelled on 9MAR43 due to weather.However some organizations did fly "patrol and transport" operations.
It is possible he was lost on this date.I will advise if there is a way to find a MACR (Missing Aircrew Report) that can be associated with his name.