Tenant disappeared with arrears and can’t get deposit?

We have had a tenant vacate a property unexpected. Verbally over the phone the tenant has told us he has left and the deposit (£600) will cover the rent arrears of (£500) plus the damages to the property they had left.

When we finally got possession of the house back the estate agent who did the tenant find and organised the AST is saying that without written consent they can not release the deposit back to us and we must take the tenant to court.

Has anybody come across this before?

As far as I can see the well known high street agent is sat on the £600 – the tenant has vanished leaving behind a lot of mess knowing he owes the final months rent so unsurprisingly his phone no longer works.

I am reluctant to try and take the tenant to court as I have no idea how to take somebody to court who I have no forwarding address or phone number for…. Surely I am not the first person to have a disappearing tenant and an Agent refusing to release the deposit or even let us dispute the deposit…..Any advice welcome!

James