I did tell the guy that it was more than likely water sensitive,did a burn test,pale grey ish ash,yellow flame,have just told him it`s a replacement,he is going to have trouble finding it i think.
I did extract the rest of the landing,so as not to leave a clean patch,and that dried in front of my eyes,without any issue,was only 8x4 so it shouldn`t cost him too much,they did change the downstairs room,which was the same,prior tenant defrosted freezer,and it leaked all over it,and left another huge mark.
Underlay was not stuck to floor,just the backing of the covering.