Yep, that's right toilet frogs!

Was around at Mum's last week, went to use her 2nd loo, lifted the lid and got a huge fright, big splash in the bowl and a pair of disappearing feet. The bowl was also in a bit of a mess, (Mum would normally never go in here), cleaned the bowl up and told Mum.
No sign of frog for about a week, then Mum goes in to check the other day, and there it is sitting on top of the lid!

Mum, quickly closes the door and wedges a cushion in the gap at the bottom.
I go around the next day, thinking to find a dead frog, (they can't breath if they dry out too much).
No sign of it, look behind loo, not many places to hide in loo, so mystified I raise the lid, and there it is in the bowl!!!!!
Before I can react and grab it, there's the disappearing feet thing again.

Mum has put white king down both toilet bowls and weights on the lids. So far I haven't heard of any more appearances.

Do you think her solution will work?
Anybody else come across frogs that can open toilet lids, getting out and then letting themselves back in?

I'm wondering if we have some sort of evolutionary sewer system frog here. I didn't get a real good look, pretty big, about the size of the averages ladies palm. Could it be a cane toad?