I have had this problem with at least three properties within the last two or so years and one in particular on at least three ocasions ( the Sheraton Suites - W Cypress Tampa)

I have been able to get the folios eventually each time but after a somewhat forceful insistance by escalating to the manager.

While I agree with Lurker II that one could always get this info from spg.com
it seems pretty silly and really should not be necessary to have go that route. If the property has a record of your stay there should be not problem providing it.

mike