My companion needs guidance on a land bargain that went south

Hello everybody,
My companion needs guidance on a land bargain that went south . Their home was recorded available to be purchased, and a potential purchaser put down a deal, marked an agreement with a store down. Anyway they retreated from the agreement. The purchaser who put the store down needs their store back , and the vender of the house thinks the store is presently legitimately theirs. The property holders need to carry this to court yet doesn't have the contact data to serve the ex-purchasers. Realtor, shutting legal advisors on the two sides will not deliver customer data because of security reasons . My companion employed a suit legal counselor and he proposed the main way is to enlist a private specialist to get their location to serve them.

Anybody at any point been in this sort of circumstance ? Is there a simpler method for getting the purchasers information without employing a PI?

Ontario , Canada