Patio sealer disaster - how to remove?

[onionsa]

Hi all, someone put a patio sealer on our former concrete flags and it’s not taken. It comes up all white when it’s wet, almost like a plasticy pva look.
The guy never told us what it was, never honoured the warranty, beat his wife and then shut down his online accounts, so getting information is effectively impossible.

Does anyone have an idea as to what might have been used that would react like this, and what I could try to get it off?

Thanks in advance.

 

[Wayners]

Sounds like PVA.
Does it go sticky as well as turning white?

 

[onionsa]

No it’s like a plastic on rubber when you run a trainer against it. Doesn’t go sticky at all.