From what I've seen, encapsulated-aluminum disk bottom pans and straight aluminum pans are simply prone to warping. The aluminum is just too soft and can't take the mechanical stress, and the disk-bottom pans have problems with dissimilar metals. Different metals expand at different rates, and thus will separate over time if heated and cooled repeatedly.
Now, it's possible to get a disk-bottom pan that won't warp or separate, but the outer jacket of stainless must be quite thick, at least 2 mm. The disk in the bottom also has to be completely covered by the steel -- if you can see a different looking metal peeping out, the pan is a no-starter for you. It'll probably be a heavier, thicker pan, with fairly thick walls as well.
The simplest solution is to use a pan that's cast-iron, all-stainless, or multi-ply AKA clad aluminum/copper. Cast-iron is too thick and rigid to warp, and is a homogeneous material, so it isn't prone to problems from dissimilar metals. All-stainless is stronger and more elastic, and again homogeneous. It has lousy heat conduction though.
Multi-ply pans avoid warping because they're better made and incorporate thicker outer layers of stainless, which hold the pan rigid against warping. I think the process by which the aluminum or copper is contained in the stainless is also more robust.
It will take longer to heat than a thin metal bowl. It probably wouldn't crack, being oven-safe - it's just being exposed to steam, not direct flame, so long as it is above the water, not sitting on the bottom of the pot (which is what you describe.)
Best Answer
I don't believe small, cosmetic scratches are a problem -- Those will happen over time and use anyway, and don't affect the cooking abilities of the pan. If you scratch through to the metal pan underneath (assuming it's cast iron), that would be a problem, and depending on the manufacturer you might be able to get it repaired/replaced.