Yup, similar thing happened to me many moons ago, 86 or summat... my band were rehearsing at a small club in Wokingham called Angie's, they used to let the place out as practice space during the day and then put gigs on at night. Anyway, we were close to packing up when this guy wandered in at the far end of the club. "Oh sorry" he said, "I'm not interrupting am I?". We assured him that he wasn't, but he offered to wait outside -- charming, polite chap he was. "Nah, it's ok" we said, "We're just packing up."
"OK" he says, "my group is playing here tonight, thought I'd get here early to see what it's like... oh, name's Herbie Flowers and I'm pleased to meet you all..."
You can imagine how far my jaw dropped.