I'm bored and sick of laying in bed so I took a brief tour and I came up with a possibility for an id. I use the term ID loosely, as I think their are many hundreds of thousands of marine snails and I didn't do any real search that I can be proud of.
Update: found it last recently so got it out of the tank to get some footage. Sorry for the movement, I am not great with the digital microscope.
It grew quite a bit. With magnification I can see it has a spotted foot and spotted proboscis. It seems to only come out at night after lights out. I don’t know enough about snail proboscis to say if it is unusually shaped.
This one might require a specialist. The closest match I have found is Hesperaptyxis luteopictus (painted spindle snail). But it's still very different...
Maybe just a different species, maybe it's a juvenile snail and will change it's appearance quite a bit later on. I don't know, sorry
Thank you both for having a look at this with me! Really appreciate it. Since this one came from indonesian live rock I’m not surprised there could be difficult to ID critters on it @EnterName That snail looks similar indeed but I can also see a lot of differences. We’ll have to wait for it to grow and see if it changes any I guess. Thanks though!
By now the snail has grown a little bigger and I see it pop up sometimes now because it is becoming harder to miss.
Some additional info:
It seems to be hiding mostly underneath the sand during the day, then in the night when I see it it is mostly on one rock. I tried to drop a mussel/spirulina fish flake nearby it and it fled in terror. I tried a bit of shrimp when I had it in an observation glass but it sped up movement and rushed past it. I don’t know if that means it does not like meat or if it is just scared, but I will continue trying to get more behavioral observations. Meanwhile it is growing well so I’ll post another photo update if I see it in another month or so. We’ll see if I can find out what it is actually eating