Just before Christmas I was working an old shelf queen (Hasegawa's VF-0S from the anime Macross Zero) and I dropped one of the main wheels. Long story short, 4 hours later study completely cleaned and wonderfully swept (floorboards, no actual carpet monster to fight) including moving desks, room turned upside down twice and still no wheel. I've spent less time looking for (and finding) 3mm photo-etch parts in shagpile carpeting.
Option 1: Finish kit with wheels up or 2: Buy some moulding and casting material. I'm going with option 2 and trying a newish item on the scene called Oyumaru.
Oyumaru is a reusable thermo-plastic like material. The reusable part here is the handy bit. While it may not be as useful as silicone for moulds of very fine detail, its great if you just want to make one or two casts of some equipment or say an ammo box and then reuse your Oyumaru for another project. I'll include a post in the coming weeks with photo's on its use.