Travis Kelce missed out on the chance to snag an autographed Taylor Swift guitar on Thursday ... but he's "Mr. Perfectly Fine" about it -- 'cause he already owns one!!
The Kansas City Chiefs tight end hit Las Vegas to support his bestie/quarterback Patrick Mahomes' charity event auction ... and at one point in the evening, an instrument signed by his pop superstar girlfriend was up for grabs.
35-year-old Kelce -- who went stag to the festivities -- initially stood up to express his interest in bidding on the item .