Vomiting question

I left my apt for a few hours today and when I came home I saw my cat had vomited. Apparently she decided to cover said vomit with one of my shirts that was laying on the floor...maybe she hates that shirt? Anyway, tonight since I've been home she has been eating and is playful, doesn't show any signs of sickness. There is nothing around my place that she could have been exposed to and her diet has been pretty much the same. I did buy her some canned Iams last night and she's never had that before but ate it last night and was fine. Could something as simple as a different cat food be the cause? Anything I should look for in her behavior, etc? I think she is fine but I've had her over a year and she's never thrown up so just wondering what to do now.

It's possible that the food didn't settle on her stomach well. Was the vomit just food or was there hair in it? If there was hair then it was likely just a hairball.

Keep an eye on her, if she shows any signs of being sick, behavior or appetite change, or vomiting again, make a vet appointment.
For now I suggest not giving her any more of the Iams in case that was the cause.

My kitty Sho has problems with certain foods, some canned foods would upset his stomach too.

You kitty probably tried to hide it because it smelled bad, though why she chose one of your shirts is anyone's guess maybe it was a familiar/safe scent?