Hello maa123,
Thanks for using our plugins and welcome to the forums!
I’m really sorry about your issue. Unfortunately there is no other way of bringing back deleted event categories and their assignment to events then restoring a database backup.
There is no trash for the taxonomies like categories and tags, they get deleted.
Although this might not be the answer you were hoping for I hope this clarifies.
Let me know if there’s anything else I can help you with.
Cheers,
Andras