Yeah I don't find it weird to not wear/bring your engagement ring on trip to be honest. It's easy to lose it. I don't mean robbing but staying at hotels and outside of your normal environment it's easier to lose things or forget to take it with you. Definitely forgot to take my watch one time when I was on a trip, I already checked out and was on my way back home when I remembered I left it on a stupid place "where i won't forget it"
of course i forgot....
So i'm not surprised she didn't bring it, I probably wouldn't either. I'm sure she discussed it with her partner. It's not a big deal tbh.
Also flying can really swell your hands. First time I flew i didn't expect it much, so i wore a legging, I almost burst out of the seams after a long-haul flight