Is there a reason why you're removing some of the groups I'm
cross-posting to?

AMUN wrote:

It's also very possible the cat never ate the pill, but spit it
out somewhere else.

I was watching him eat via a closed-circuit web-cam that I set up in
his room, and when he was done I had a closer look and found no
remnants of the pill on the dish or anywhere nearby.

As usually the pills simply dissolve the worms so you won't ever
even see part of them in the stools.

I thought that the pills kill the worm or impair it's ability to
continue to clamp onto the GI tract, and hence free it up and allow it
to either exit with the stool, or in this case to be vomited up.

Only sure way is to grab the cat and shove the pill in it's mouth,
then hold it's mouth closed until it swallows it

Like I said, I was watching it eat, it did not spit anything out while
eating, and there was no pill remnants to be found.

As you say the beast got dewormed when you first got it, it's
strange the worms re-appeared when the cat was kept indoors.
As tapeworms are almost exclusively caused by eating infected
fleas.

Yes. I told the vet to give him a worm pill while he was recovering
from being neutered, and Drontil is listed on his health card, and so
is a Revolution treatment.

Again it may have really been badly infested, but even the worst
I ever heard of got knocked out after a second dose of tapeworm
pills. Clean up, as it sounds like you may have inherited at
least a small flea infestation with the cat, and they may be
re-infecting it.

After he vomited the worm, we cleaned the room (laundered the canvas
floor covering, wiped down all surfaces, etc) and put him back in the
room. I'll have to give it a few days to see if he's approchable
enough to give him another Revolution treatment (assuming the vet did
infact give him an initial treatment 11 weeks ago).