I have moved all of my octos when they started out too small for the larger tanks and have never had a problem moving teen/adults. It is just the tiny ones that seem to be very, very sensitive to water changes.
That is certainly our hope, that it’s just in a rock being shy! Only time will tell, so we’ll just keep up with maintenance and wait for the tax return so we can get some Kessils for growing ricordea and zoanthids.Odo was so young it is hard to make any kind of call. Best case (and quite normal) is that she/he is holed up in the LR. Be sure you keep plenty of small crustacians (pods and hermits and you might try keeping some live shore shrimp in the tank). Worst case, she/he was so small that death did not disrupt the tank. Experience makes me tend toward the first guess. They typically stay hidden until around 5 months old.