All chain stores (including Wal-Mart) have a policy adjustment fund just for this type of problem. Go see the store manager, politely explain the issue, and ask for satisfaction. You may be surprised.
I have seen this type of staining on the best quality linoleum, it is due to the poor quality of rubber backing on the mats, not the lino.
In the future, it may help to minimize this problem by putting the mat in the clothes dryer first. This will help eliminate the aeromatics in the rubber backing.
Good Luck!
Dodgeman