Find out the region lock of the key

If he did this, he is a real monster.

https://steamdb.info/ -> search game -> Packages -> If theres package that has something like "only in 12 countries" and when you click that SubID and it says UAE then it can be that

For example Monster Hunter Wilds has package https://steamdb.info/sub/1196087/ that only lets the key be activated in said countries.

Other option is to go to "deals" section here and search the bundle and see if theres anything written about region locks.

Someone also mentioned that you can contact steam support and ask when has the key been activated - if it was near the time of trade...well..

Or just contact store you got the key from

how about the steam support?

first of all: never trade something relevant with someone who doesn't have a reputation to care.
that said, you have no way to be sure about what happened. the guy could activate himself or give it to someone else to activate. there's no info available about when or who your key was activated. discovery the region locks of the key is the best you can get when you try to activate the key yourself (with steamdb addon installed).