Upvote:1
When you left the US , the airline should have collected your I-94 and submitted it to the CBP. That apparently didn't happen, but from your post it's hard to tell what exactly happened to your I-94. Could be that airline didn't collect it, that the airline misplaced it, that you just took it home with you, etc.
Check out some advice no how to proceed for a few different scenarios.
https://www.immihelp.com/returning-uncollected-i94-form-to-cbp/
You will have to dig up some proof that you actually left the US. The link gives a few examples of what might work there.