The guy thoughtfully offered to check with the hotel and get back to me, and he e-mailed me after calling them. He says the hotel had a record of my credit card and SPG number being put on the room, alongside Heather's name, but that neither of our cards was ever charged. "The charges were all picked up by a master bill for the group or company you were staying with."
As far as I can tell, after checking all of my credit cards' online statements, I was never charged by that hotel. I'm waiting to hear back from Heather whether she can find any charges. If she was charged for the whole thing, you'd think she'd have let me know I owed her some money! But if neither of us was charged... then what? Do I indignantly make them figure out who paid our hotel bill so we can throw money at them? :-)
Meantime, as with my screwy experience with HHonors this past winter, SPG has reinstated my account and the guy put in a request to reinstate my points (13,000 or so). I've never redeemed any points, but I guess a free night can be as little as 2,000 points, though the fancier hotels go up to as much as 35,000 points/night. I just don't have occasion to stay at a Sheraton or Westin or the like all that often, though I certainly have no objection to them. They just tend to be in the wrong places! I'm not sure I stayed in a Starwood property even once between Burlington in 2000 and San Diego in 2009.