Mother gave son money to pay for some of his house, would a title search show his wishes, if any, for mother?

You did not mention the title to the house. Was it held jointly with the spouse? If so, then the house passes automatically to the surviving spouse.

I am sorry for your loss.   The only other document that may have been filed was a Note evidencing a loan, much like what a mortgage company would hold.  Do you know if one was ever executed? 

Here lies the problem:  did Jane sign anything when she lent son the money to indicate that it was a loan or a gift?  Sometimes banks require a gift letter from the person lending the money.  This way there is not another competing agreement to pay out there that has to be figured in to the equation for the lender.

What you did not explain in this question is if there are children.  If her son dies intestate - without a Will - and left only a spouse but no children his Mother would be entitled to a portion of the estate under the Intestacy Laws in Pennsylvania.  That may be why his Wife suddenly took the house off the market. Here is what would apply if there is a spouse and no children:

If the decedent was survived by his or her spouse and had no surviving children or parents, the surviving spouse receives the decedent’s entire estate. However, if the decedent was survived by his or her spouse and one or both parents, but had no surviving children, the surviving spouse would be entitled to the first $30,000.00 of the estate, plus one-half of the remaining estate, if any." And the parents , I believe, would get the other half.

Seek legal help with all this.  There may be something else under the law in your state that you can do depending on what you have to evidence the loan.