I'm really intrigued here as I've had this "problem" before and it was either one of two things as Animal Mother said, it had gotten out or it was a female and it laid eggs. I didn't have a red dwarf, just a "plain ol' octopus" though.
no no luck
but i just realized that about 12 of my blue legged hermits have disappeared i am very curios to know ware they have gone
is this octo still in there? like my tank is completely open on the top now and has been for about a month i dont understand
IF the dwarf was a mercatoris, it is quite likely. Not much octoproofing is necessary and if they have good hiding places in the live rock and plenty of food they can disappear for long periods (one of the reasons I recommend smaller tanks for them). MIA (Missing In Aquarium) would disappear for weeks and then decide he wanted a shrimp treat. I was never sure when he actually died. Wiley was pronounced missing and assumed dead at least twice and is now going on 13 months old and finally installed in a smaller tank.
... with a lot of luck . I still don't know why I found Wiley at the front of the tank one night. I would look for him nightly without a spotting and then he was just sitting out in the open one night and I had a net handy (on purpose but I had give him up for dead for weeks, at least twice). I had not been feeding the tank and perhaps he ran out of food in the rocks but I can't be of help there. You might try putting a cluster of barnacles or a small conch shell at the front of the tank to see if he finds it to his liking. Putting a fiddler in something clear and easily accessable might tell you that he is alive. Neither worked with Wiley, however.