I have credits for all my flights, but a few recent ones are someone else's itinerary!

That is: I flew IAH-SAT with confirmation number C***** on 1/23, but my TravelBank page shows a IAH-FLL flight with confirmation number A*****, which was my trip to CGN in 2006. Also, an OAK-AUS trip got credited correctly, or at least as OAK-IAH (the IAH-AUS segment was diverted back to IAH). But the same confirmation number shows up again in December as a CLE-ORF flight, and I've never even been to ORF.

Does anyone know what's happening there? Does CO reuse confirmation numbers that often?