I think what the OP is trying to say is that the FA said there is no record of an infant being on board...period...in any cabin (E-, E+, or F) and if the boarding pass was indeed scanned upon boarding, then there should be a record...hence making the FAs comments somewhat odd. Switching seats between Y and F is another issue that's probably been discussed MANY times on other threads in this and other forums...personally, I don't see what the big deal is and we all know it happens ALL the time....husband gets upgraded but not the wife so he kindly switches, people see military onboard and give up their seat to move back to E-...I can't say that I've ever seen a FA with enough gall to ask a serviceman or woman to move back even though they were not "entitled" to the upgrade per UA's policy.