Help! Verification of previous rental but lost contact with previous landlord. (record, transaction)

[Omns]

I subleased a room without any paper contract previously, now I need to do verification of rental but I can't contact with my landlord. For some reason he has changed his phone number. How can I proceed the VOR?
I do have some transaction history from my bank history record, and I have some letters can verify I've been lived there, but are those evidence enough for the verification? Thanks for any suggestions in advance!