1978 Mint Set - Missing D Dime

I thought at first the D Dime slipped out of it's sleeve. But upon investigation, the seals on all four sides of the dime are intact. No openings. The only other anomaly there's no seal between the quarter and half, and the quarter is sealed in it's place, I can't slide it. With literally a thousand mints sets searched over the years, never seen this before! Has anybody else? Guess it's too late to ask the Mint to send me a replacement set!
Kevin