Stimulus Check Received by mistake.

Hello,

I was in the US as a student for more than 5 years on an F1 visa. I always filed my taxes as non-resident alien using the 1040NR form and a platform called Glacier. In 2018 I moved abroad, and in 2019 I filed the taxes for the year 2018. However, the usual platform was telling me that I could not file the taxes as non-resident alien anymore and that I had to file the as resident-alien since I fulfilled the Substantial Presence Test, and that I had to use the standard tools to file my tax return. 

With this information I used turbotax to file my taxes.

During the month of May I received the stimulus check. I know that there was a mistake and I am about to send it back. This event made me think about my current status. 
Can anyone help me with this situation? It appears that I appear to be still an alien-resident to IRS, when they actually know I don't live in the country anymore. What should I do?

Thank you very much for the help and support.