Today I learned more about margin requirements SNAP stocks

I checked my account and found that my short position in SNAP was covered. Called TD Ameritrade, and they told me that it was an action by the firm. Apparently, it was a forced buy to cover, since SNAP shares were being sold, and the firm had to correct their balance. Has anyone else experience something like this?

This sounds like it has less to do with a margin call and more to do with it being a short position. Is it possible that TD Ameritrade force closed your short position because they were running out of shares to lend and and needed to replenish their reserve?