For a security to be "shorted" is must be a marginable security per Regulation T.
As for the issue of where your stock sits, I sense you are bumping up against the "I don't want to let shorty steal my shares" conspiracy narrative. If that is the case...can't comment. Nobody can "steal" shares from your account. If we are talking about keeping your shares from being used for a short by someone else...I will leave that to others...but again we are talking about something for which there is zero evidence of occurring here in any meaningful way.
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