The vast majority of homeowner's policies in the US use form "HO-3", which specifically does not cover motor vehicles. For just one example, check out http://www.mcgrathinsurancegroup.com/home/ and click on the link on the left called "Property not Covered".

Discussing the question with your agent or company is certainly the best advice, but the most likely answer will be "it's not covered."

Robert, is your auto insurance with Allstate as well? That might explain the overlap.

(Coincidentally, this topic happens to be on the next actuarial exam I will be taking.)