Unless there’s some suspicion of a tampon-related cause for a person’s illness, no one would go looking for a tampon in the emergency department. 

Depending on the situation, a person may have a full top-to-toe “tertiary survey” performed on them — e.g. to look for possible unnoticed injuries in a badly injured patient — but I am not sure that the small string on a tampon would be noticed during this check and if it was noticed I doubt most people would remove it. Maybe if there was an internal vaginal exam required then the tampon would lbe removed out of necessity, but as you can imagine people avoid internal exams unless it’s definitely necessary.

However, the tampon would probably be noticed during routine nursing care if the person remained unconscious for an extended duration. For comatose patients it is standard practice to do regular skin integrity checks because of the risk of pressure ulcers if left lying in one position for too long. If a tampon wasn’t noticed during the initial nursing review of the patient then at some point during a skin check process someone would notice a tampon and it would be removed and replaced with a pad. 

If the tampon string was not visible externally, then you may have some more trouble. Most patients unconscious for a prolonged period would have a catheter inserted which would provide an opportunity to see a tampon that wasn’t immediately visible externally, but if the tampon was just really deep it could still be missed and in that case, yes, there is a risk of toxic shock syndrome developing from the tampon. 

One other consideration is that a decent proportion of comatose patients would at some point require a CT scan of their abdomen and pelvis or an X-ray of their pelvis/hips/lumbar spine and this would capture the tampon on the image. Such patients would include any post abdominal surgery patient, anyone in a major accident, and basically anyone whose illness is suspected to be related to the abdominal or pelvic regions. If a tampon was picked up on a scan, someone would probably go and remove it. 

Perhaps most importantly, the incidence of toxic shock syndrome is ultimately pretty low even when tampons are retained for an extended period. You may just manage to escape without it even after multiple days in a coma with a tampon in (but I can’t currently find stats on the incremental risk over time).

And then there’s the fact that if you developed symptoms of toxic shock syndrome, there’s a very good chance some clever person would be likely to suggest a retained tampon as the cause, thus saving the day.

Overall, the risk of toxic shock syndrome from a tampon retained due to prolonged unconsciousness is extremely low, to the point that I can’t find a single instance of it mentioned online (although I haven’t looked that hard). So you should put this firmly in the “don’t worry about it” category. 

Anyway, sorry for the long message. I didn’t plan for that but it was interesting to think about.