Babysitter. It was listed on some of his early bios, and Solondz once personally confirmed for me that it exists, but that's about it. The IMDB even removed their listing for it. But any mystery surrounding Babysitter can now be considered solved, as the entire nine-minute short has been uploaded onto Vimeo for Le CiNéMa Club!
It's a surprisingly high quality transfer, and for a student film with no synced sound, it's also surprisingly entertaining. As opposed to Feelings, which comes off as more of an interesting early exercise by the filmmaker, this one's engaging in its own right. You can feel his distinct writer's voice in the work; and it's entertaining enough that it's really worth the watch even if you're not a die-hard Solondz fanatic. Maybe the next time Criterion or another high end label gives one of his films the special edition treatment, they could include this and his other short films as bonus features.