If the seller'sdisclosure didn't include foundation work, it still will not mean he is at fault, as the work might be done by previous owners. Anyway a couple of ways you can try:
1) contact City permitting department asking for permit record. Foundation work requires City permit, so you may see the record past repair/renovation work done to this property.
2) contact a few foundation companies of your area, asking them if/when they have done work to this house. They may have kept record. Try to ask tactfully.
First of all, get a professional to do a check and provide you with a quote to see if it IS a big deal.
