If she builds and ovulates, there's a good chance that he was breeding with her when you weren't looking. I paired a pastel with my tiny male pied last year, and only saw them lock once. But she produced 6 big eggs. So he still got the job done.

(But the same pied male completely ignored my black pastel female last year. I honestly don't know if they don't like each other, or if she just wasn't ready to make eggs that year. She never ovulated at all. I wonder if she would have with a different male?)

There was one person who posted this year about a virgin female who laid a clutch of slugs with one fertile egg. So sometimes they do produce little parthenogenesis clones of themselves, in the absence of viable sperm.