Can seller sell their home to relo co. after agreement w/us

After our agreement with the seller to purchase their home for $819,000, and receiving the sellers disclosure 2 days later, we got this new form called "addendum to purchase agreement". On the 2nd page it says "seller is a relocation management firm. This transaction is subject to seller purchasing the property from the prior owner and becoming the contractual owner of the property".... At the bottom it says seller, Hewitt Relocation services. First, they weren't the seller, we had the agreement with. Does that sentence make any sense? They say they are going to be the seller, but they are not really yet. So how can we sign a contract with a seller who really isn't the seller? Maybe they could be the rep or POA, which they don't aclaim they are, but is this legal? Also I think we had given them $5,000 to seal the deal, which we would have lost had we backed out because of this relo thing. Also the Fryes did sell to Hewitt Assoc. after our agreement, selling them title or deed, I am not sure which. Can they do that in the middle of a deal? Many things were done wrong such as forcing us to use a particular title co., many latent defects, didn't respond about the contract agreement in a timely fashion, so we lost our ability to use our federal credit agency, because they wanted the closing to be by Nov. 30. We then had to go with a Freddie Mac who could expedite our loan in 15 days, who sold our loan a couple times and have been a real nightmare. I wouldn't have minded all this so much, accept we are having serious plumbing issues (as well as roof problems, AC, etc. also got an assessment for $4500 due in 60 days 4 months later. The house was built July 2001. We bought it for $819,000, in nov. 2005, so expected it would be free of the defects it has. Visually it is beautiful. The piping, plumbing might have to be completely dug up because of this creepy smell, and the continual back ups, and even having to have a floor replaced from this slow leak from the toilet.
We did close on the 30th of Nov. and so I was also wondering why the closing doc charged us a day from Nov. 30th to Dec. 1st?