Luggage returned within 24 hours. Very typical.
Couple of points.
1 There are two forms of "gate checking"
Typically bins fill up, you cant stuff your carryin in overhead, FA takes your bag, it is attached to your passenger record and FA/GA gives you a gate check tag tag identical to the one at the ticket counter. Your bag looks exactly like the 'big boy' luggage that people checked in at the front counter FAII.
On Regional jets - roll-on luggage does not fit into overheads, so you leave it on jetway. You attach a gate check tag to your luggage, you tear off (or Photo) the number. This luggage DOES NOT attach to your PNR (ticket) and you hold the only record of its existence in your hand. UA or UX has the same responsibility for this luggage as checked luggage, but if you dont have that tag......YMMV
2 Computers, cameras, etc in any checked luggage is a BAD idea.