SMA PLT ACCUSED OF FAILING TO CANCEL IFR FLT PLAN.

Narrative

WAS ON IFR FLT PLAN FROM N99 (BRANDYWINE) TO FDL. AT 5 MI E OF EMI VOR; I WAS INSTRUCTED TO CROSS OVER EMI AND PROCEED DIRECT FOR THE ILS 23 APCH AT FDK. I WAS INSTRUCTED THAT I COULD EITHER CANCEL THE IFR FLT PLAN ON THE CURRENT ATC FREQ OF 126.75 OR CANCEL ON FREQ 126.9 AFTER LNDG. I ACKNOWLEDGED. WHILE MAKING AN ILS APCH; I WAS ASKED BY ATC ON FREQ 126.75 IF THE ARPT WAS IN SIGHT. UPON CONFIRMATION BY ME I WAS INFORMED BY ATC THAT MY IFR FLT PLAN WAS CANCELLED AND INSTRUCTED TO SQUAWK 1200 ALONG WITH FREQ CHANGE APPROVAL. I CHANGED SQUAWK; CHANGE FREQ; AND CONTINUED TO LAND. I MUST NOTE THAT I WAS BUSY AT THE TIME AS I WAS ON THE LOC. TO MY ASSUMPTION; THIS CANCELLED MY FLT PLAN. LATER; I CONTACTED BWI DEP ON 126.9 FOR THE IFR CLRNC TO MAKE THE RETURN FLT. AT THIS TIME I WAS ASKED WHEN I LANDED AND WHY I DID NOT CLOSE MY FLT PLAN. I PROCEEDED TO TELL BWI CLRNC WHY I THOUGHT IT WAS CANCELLED; BY GOING THROUGH THE STEPS THAT OCCURRED. I DID NOT RECEIVE ANY FURTHER COMMENT AND PROCEEDED TO RECEIVE MY CLRNC FOR THE RETURN TRIP. I MUST CONCLUDE THAT THE ERROR WAS MINE; AS I DO NOT REMEMBER IF I SPECIFICALLY CONFIRMED WITH BWI APCH ON 126.75 THAT THE IFR FLT PLAN WAS CANCELLED.