Doesn't mean you were actually vulnerable.
Sounds like the embedded SWF that your computer downloaded had something inside of it (maybe signatures, probably heuristic) that your AV detected as a threat.
However, for the exploit to work Flash has to actually be vulnerable. If you're running the latest flash, this is unlikely and even without the AV you were probably fine.
Flash is pretty good these days at keeping exploits patched, unlike Java.