AI Assistant Unrecoverably Erases Overlong Questions

I was preparing a long question for the AI Assistant. After I was ready, and had collected all of the information I needed to ask a good question, I clicked the send button, and I see....

This input is too long — try splitting it into smaller parts.

...but it's already erased my input for some reason(?!) so it's all lost and unrecoverable. Undo doesn't work. Back doesn't work. It's just gone.