According to Wikipedia, the Meiri was rediscovered in modern times. I assume that means in the 20th century or so.
However, Hebrewbooks has a copy of the Meiri from 1795. I don't know if that was the first print, but even that gives quite a few years for it to have found its way (or at least discussed) in "mainstream psak" (meaning not Chazon Ish generation but Rabbi Akiva Eiger/Chasam Sofer generation).
When was it actually discovered, where there any "early" discussion as to its validity and was it quoted by 19th century poskim?