Yes, they can! They can essentially use these bones to amplify their existing magic, helping to make their barriers stronger, for one. They can also use it to heighten their everyday magic, like using the bones to help them power 10 pieces of electronic technology instead of one. The other two Palai genders won't be able to utilize these magic bones at all.

There are Uvi remnants lying about -- you can find fragments of their weapons at varying degrees of damage falling from the sky, for instance. The Uvi don't lay eggs and are instead live birth creatures, and their habitat is extremely minimalistic. Characters can find small items the Uvi picked up from Palai houses, but nothing especially newfangled -- there will also be ripped fragments of their clothes that didn't disintegrate. As for living stragglers, the Uvi need to spend a lot of their time in their seaweed so it can be assumed that they're all dead. If one or two stragglers are around in the water, they're doing a very good job of hiding, but the possibility isn't completely off the table.