I used to remove asbestos for a living. Even if what you've got has asbestos in it, I wouldn't worry about doing a bathroom. Keep it wet with soapy water as it breaks if you're really worried about it, but I wouldn't.
Heat will help. Scrape up what you can, a long handle will help, then use a heat gun on the tough parts.
What do you do if the mastic also contains asbestos?
Scrape it up and not worry about it. Put it in your kitchen trash bag and toss it in the can. We used to wet it down with something nasty (I can't remember now hat it was) and buff the floor with a buffer and coarse pad, then squeegee it into snow shovels and bag it up.
It's the fibers in asbestos that get you. If a human hair was 40' in diameter an asbestos fiber would be 1/2". It takes a lot of exposure to build up scar tissue in your lungs. Fibers contained in the mastic don't break free as easily as something that crumbles. The surfractants in the dish soap will help break down the surface tension of the water to keep the fibers from getting airborne.
We had to wear air quality monitors while working and NEVER had a sample come back on a floor job that would've required us to even wear masks by OSHA standards, for what that's worth. It's just one bathroom, scrape it and don't worry.
The real harm in removal is in industrial applications where it was used as high temp insulation. Over time it breaks down and when you break it free it'll usually crumble, some of it just poofing into a cloud of killya. You really do have to be careful with that stuff. The big tanks are done in a fully contained negative pressure poly enclosure with battery powered positive pressure full face masks. THAT'S miserable work. They kept the machinery running until we were done and we had one job with a guy who's only responsibility was to keep patching holes in the poly wall that kept melting (it melted at 350*).