What happens if you put a capacitor in the wrong direction for a short time?
You didn't say what technology the capacitor is, but considering it's 6.3 mF, 50 V, and polarized, I'll assume it's a aluminum electrolytic.

Yes, the capacitor has gotten damaged, at least somewhat.  How badly damaged, and how irreversible the damage depends on what voltage was applied for how long.  A 50 V capacitor can probably take 5 V in reverse for a few seconds, and probably mostly recover when promptly forward biased.

The prognosis gets worse at higher voltage and longer time.  The insulating layer formed on the surface of the aluminum gets eaten away, so eventually there is a short.  You have already damaged the insulating layer somewhat.  It can actually heal somewhat when forward voltage is applied, so it's hard to say how bad the damage is.

If this is a commercial application, toss the capacitor, replace it with a new one, and don't look back.  If this is a hobby application where you can tolerate the capacitor blowing up or leaking in the future, then continue on and be more careful next time.

To paraphrase Dirty Harry: "Do you feel lucky?  Well do you, punk?"