It appears that Mexico offers visa-free entry for tourism/business/transit for holders of valid unexpired visas for (among other places) the Schengen area.
If your Schengen visa is still valid, you should be fine. There's no indication that Mexican authorities will attempt to make their own investigation into whether the Schengen visa should have been issued originally. If they wanted to do that, they would have an actual visa requirement of their own instead.
Basically they're using "able to get a Schengen visa" as a proxy for "doesn't fit the profile of an economic migrant", since a known tough consular service must have determined that in order to issue the visa (or, in cruder terms: "would have better options than Mexico if they wanted to be illegal immigrants somewhere anyway"), and concluding from it that it's probably safe to let you in.