"Adjusted Rinny's bellybutton"...
Interesting.
Not sure why inventory upgrades would be needed... you're able to hold 99 of every item. (Where is Lust even keeping it all? Ain't no way all that's fitting in nature's pockets.)
The fortune teller in the black market is a good place to go if you're missing anyone. If you are, she'll tell you a vague description of who, then you're on your own.
Otherwise... there's the wiki... which usually turns up as the second option in whatever search engine you have.
Found a rather odd bug to report. I left Rinny in the pillory, then came back into the dungeon to free her. She was nude when I stepped on the tile to leave, to which I thought "Ok, that's not normal, even for her". Then I saw that she was still my companion as I was roaming the abandoned town. I went to Transylvania, then immediately left to see if that would fix it... and she did stop following me... but she was still naked. She only put her clothes back on after I left, came back, and "had some fun".
Sorry if this is a bit long... tldr: Rinny is streaking.