This is kinda comical to me. I believe I have the gelding in question. I've only ha him for a month, but I can definitely tell you he's had no studly behavior whatsoever. He's actually 10-12 years old, contradicting the Coggins that were given to Tori. He does have loose skin in his nether regions, but it happens sometimes. I've never seen him drop, ever, even around my mare. He gets along with my proud cut gelding perfectly. My gelding, who is actually a 12 HH pony, is lead, and Gulliver minds him perfectly. Gulliver has perfect ground manners, and has never shown any aggression or stud behavior.
Now I believe Tori had Gulliver about a month. I've only had him for a month. In that time span, we have never suspected him to be a stud. At all. And I think you forgot to mention your mare is in her 20's? Maybe she just won't come into season any more. Who knows? Maybe a stud jumped the fence? Or maybe the stud that you keep on your property got in with her?
Also, it's far too early to notice foal movement. What you see moving around is most likely her gut.
There on the tips of fair fresh flowers feedeth he; How joyous his neigh,
there in the midst of sacred pollen hidden, all hidden he; how joyous his neigh