Wow, I agree 100% with everyone else. OP, keep us posted about the consequences. I do think at least one person should raise doubt with the angry mob. Just say, "Perhpas this someone lost someone close to them recently and needed to get away so they didn't go bawling in public, perhaps this person ate something that didn't sit well".
Since the person did it quietly and discretly, don't go up and ask this woman, leave it be.