Parking space illegally sold to another

Hi, I bought a 1bhk in rahatni, pune in 2014. Was allotted a 4 wheeler parking space. As society was not formed, so allotment was done to me by putting a signature on parking blueprint alongside the flat number and parking slot ID. Parking ID is used by builder to identify a parking spot in blueprint. In 2015 end, I gave flat on rent & in 2016 my tenant informed that my flat number board was removed from parking spot. After some time it was found that a new flat no. and parking ID has been painted on that spot and I went to builder they said they have not done anything. When the new flat people were confronted they told that this spot had been sold to them by another builder which owned some flats in the project. They Also have got parking allotment letter from that builder. As our society formation was not complete so I don't have parking letter. But as a proof my sign on the blueprint and my builder confirming that they have not modified parking IDs. Also, I HV old photo of same spot with my flat no. and ID. Now I'm running from pillar to post and no body claims responsibility. On confronting other builder who created this mess they ask for parking letter and say that blueprint thing is not valid. Not sure legally what is my position and what can I do now?