A kept ticket proves you were there without explaining who you were there with emotionally.

The ticket is proof of attendance and nothing else. It confirms the date, the venue, the seat, and says nothing about who you went with, what was unresolved between you, or what the evening actually was. Physical evidence records logistics, and the reason you kept it was never logistical.

If you keep such things, write a line on the back while you still remember. Who, and what it was. Otherwise you are left holding a receipt for something you can no longer reconstruct.