Yes it’s concerning if it’s been like this for more than a day. It may have an infection and need cipro treatment. Anemones tend to not do well in young tanks, so if your tank is under a year old, you may want to consider re-homing it. Otherwise, make sure water parameters, flow, and lighting are good.
It's foot isn't attached. It's deflated and it's likely consuming its self or its dying. I had a few get attacked by some emerald crabs I kept. Once the foot begins to release they generally don't make it. If it falls apart or looses tentacles pitch it.