How to access RCAF personnel records:
https://www.bac-lac.gc.ca/eng/discov...roduction.aspx
If I understand the OP correctly, his grandfather flew in Bomber Command and then was shot down over Canadian waters shortly after VE Day. The RCAF squadrons in 6 Group took their Lancasters back to Canada fairly quickly, but this seems very quick, unless he had finished his Bomber Command tour and returned to Canada before VE Day..