Sorry to hear that happened Vees. You can contact your realtor and ask them to find out some of the details. First off if it was a cash deal you can see that as a field on the SOLD MLS page. You can also validate it on the tax roll. Furthermore your realtor can pull up the amount financed if it was financed. You can even find the name of the buyer and then look at their previous location to see if it was a neighbor or even a relative.
A call can also be made to the listing agent to see what happen.
It is a pretty trivial fact check that will help explain what happened so that it maybe does not happen again.