I went to a show at MSG back in 2018 and forgot about my little keychain pocket knife I had on my keyring. They wouldn't let me take it in but held it in security until the show was over.
Problem was that I got drunk and forgot about it so I had to go back the next day and grab it. It was a $5 knife but I've had it since 2003 so I felt an obligation to go back for it!