There is no catch in place for tickets not ticketed.

UA has had reliability issues with tickets issuing since 3/3/2012. It doesn't happen a lot, but it happens enough to be noticed. Your situation is not uncommon, unfortunately. I've seen people show up at the airport for flights that didn't ticket.

If I don't expect to have time to follow-up on a United ticket issuing, I don't book the ticket at that time, or I book on Delta (they instantly ticket).

If you booked it in the evening on 5/27, it's possible you booked it, they ran schedule changes shortly thereafter, one of your flights changed slightly, and then it was unconfirmed, so it didn't ticket.

Or, they had that SHARES crash on Friday night, it's possible you booked, it crashed, and the ticketing queue purged, so any ticket in process didn't get issued. You're probably not alone.

Or it could be one of the multitudes of other reasons that UA tickets just don't ticket. I've booked before going to bed, woken up, and it's not ticketed. Nobody can explain it, CO's systems are just flaky.

As for the ETC, that is normal practice as well. The ETC is debited and marked as used against the PNR the minute the ticket is "purchased" on the website. If for whatever reason the ticket doesn't issue, the ETC has already been used on that transaction.

In fact, the times I've experienced a ticketing stall it was even more ridiculous than your situation -- my PNRs are still active, they look up the ETC, and it shows it was used against the PNR that didn't ticket!

Fortunately, the ETC issue is well known, and it's not that difficult to get them to reinstate the value and/or replace the cert.

The only time I had a bit of an issue is when I had used an ETC, the thing didn't ticket, the fare was pulled, the agent re-stored the fare at the current (higher) fare and messed up the PNR, she was going to get it manually fixed to the old (lower) fare and the ETC reinstated, I didn't have time for all this nonsense, said forget about it, note the record that it never ticketed, and I'll use the ETC another time. I booked the trip on Delta. When I went back to use the messed up ETC via phone agent, they had to do more digging to prove the original PNR never ticketed.

It takes a lot of patience to do business with UA these days.