How can we know officially the case number

Did you  get summons from court!

'Buyer Beware' applies to property deals.

It shall be appropriate to get proper legal opinion from a very able local senior counsel of unshakable repute and integrity specializing in revenue/property/civil matters before signing or making payment.

This may cost some FEE but can defend long term interest and hard earned monies.

Did you prefer to get proper legal opinion?

Visit O/o Authority under whose juridiction property falls say; MC and get all mutation records with link docs.............(preferably starting from begining ie. Shjra-e -Aks) from concerned offcial say; Naib Tehsildar , Patwaari..............

Thereafter you can move for certified copies from court..........

You are having adverse possession rights and you can file application to pattedar.  Under RTI, you have to specify the bare minimum details to get a record that is not a judicial proceeding.   You need not care for a threat and you can respond to a notice if served on you.  Protect your possession.