Are there any screen-used props or costumes that you have had the opportunity to acquire, but didn't, then regretted it? Probably MOST items that are passed up are due to cost, but how about that one that you either just didn't think to get it, or didn't realise what it was until too late?
In 1993, I worked at Walt Disney World in Florida. They had a store at the Disney-MGM Studios that sold autographs, costumes, and small props. There was a Cast Member store called "Bargain Basement" that sold damaged or clearance items at 75% off. Once at BB I saw a textbook with a cover for a school called "Welton". Wondered if it was from Lost and Found or something. Finally realised, a few weeks later, that it was a book from "Dead Poets Society", and I could have had it for $7.