ScrubsFan wrote:

Honestly, I just don't see how that could've happened. I'm the only
one who uses that bathroom and I am 100% sure that nothing other than
toilet paper has gone down it. I ALWAYS keep the lids down on both
toilets, plus there's NOTHING anywhere near that could fall into it
even if the lid was up.

I appreciate your help. Thanks. :-)

First principles:
1. "Bad" toilet - and nothing else - is clogged.
2. You didn't put anything in the toilet that could have clogged it.
3. You keep the lid down so nothing can accidentally GET into the toilet
(roll of TP, cat, etc.)

Therefo

1. Something grew there, or, more likely,
2. A rat* came up through your system, found the lid down, and couldn't
retreat sufficiently.

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*Maybe a beaver. Probably not a chicken.