Jack
Unfortunately the photos are not too helpful so lets start the, "What Species Am I" game with as much as you can remember from the purchase and acclimation.
1. Do you know the body of water that it inhabited before capture? This helps a lot to narrow the species
2. Can you give a guestimate of the mantle:arm ratio?
3. What colors did you see it display?
4. Are the eye on a well established "Y" shaped stalk or sitting close to the body so they look more independent than on a "Y"?
5. Do you see any identifiable markings under the eyes (particularly a round circle on either side of the web) or else where?
6. Do you see any color on the siphon?
7. Do you see any color at the tips of the suckers?
IF this is a Caribbean animal, I'll take a wild guess that it is O. mercatoris, a nocturnal dwarf. My reasons for this guess are the red color, what appears to be short arms (roughly 1:2.5 mantle:arm length) and the posture shown in the third photo. The arm (or both L1 and R1) between the eyes is a typical merc pose but I have seen very young animals of other species present that defense (but only mercs as adults). You can find some of the merc journals by going to the advanced search and searching titles only for the word: mercatoris.
If it is a merc, I have found that this species particularly likes to den in giant purple barnacles placed about 1/3 of the way up the water column (by embedding in the live rock). If you will place a small cluster of these at that level where you can view the openings, you will have a better chance of seeing the animal on a regular basis. Most mercs are not very active or interactive but I enjoy keeping the species and have raised a couple from hatchling.
KEEP IN MIND THIS IS A SWAG based on not anywhere near enough information
. I only offer it because I know how frustrating it is when no one will even give a suggestion to research.
Jack, Doubleposting is frowned upon. Not only is volunteer staff time extended but answers and conversations become disjoint with multiple threads on the same subject so I merged the two threads on this little one. Once we assign an ID or mark it unknown and you give it a name, I hope you will journal it and we can move it to the journals forum.