The rear engine mount isn't the problem, the failures and recall were all related to the left/right mounts. Rear engine mount failing is not a big problem, the others are.
Just check with the seller to see if if was fixed up in the recall. Or if the particular model came out after the issue was addressed.

Further to what was said above, if the model build date was affected by the recall and it was repaired accordingly, there should be a sticker in the driver's side door jamb saying it's been completed (on the front of the jamb near the door hinge I believe is the most common placement)
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We have never had a warranty issue with any of our Mazda's.
The MPS has been no exeption. One of the most reliable makes out there imho.
The front engine mount issues would be a rairity.
It all about how you treat and maintain them I suppose.