I'm just worried  that it has soaked through the grout to the concrete underneath the ceramic and that the smell will return over time,and how toxic is it?

Since most, nowadays, want you to pay them for coaching / counseling, most likely you'd be considered their sponsor rather than mentee.It irritates me when people over use the word 'mentor' especially when they should be called a coach / sponsor or counselor.

So if it was on & very hot it could possibly explode due to the phenomenon of sudden cooling but I seriously doubt it caught fire unless the fluid sprayed happened to inflammable.During our drive control trials we tested this & observed the same phenomenon (but no ignition) in the Lab at GE because of water spray infiltration on incandescents in a hot toxic environment.

It is a very toxic substance, that if removed improperly, can cause further health issues. 

The Atlanta (etc) PM situation reminds me of the US medical system where Dr's (per the AMA) can only give you toxic pills and not solve the underlying problem, which means you're in an endless cycle of going to multiple Drs getting more and more prescriptions.

"Visible" is the key word, in the colony in the unit(them) or in the crawl space(you).BTW: If the area is dry you can try using Diatomaceous earth, white powder, NOT toxic.

Something to think about while you're fumigating your lungs with toxic paint spray. 

Some of the paint cans are unlabelled and thus must be considered toxic.

They will take you to the back room where they have cans and cans of paint that is toxic waste and will usually be happy to give it to you for free.

meth labs are extremely toxic, and you will need a decon team to clean it out.