I've been looking for an item with fire damage to put on my dagger for a while, but I can't find anything. I'm only level 11. I did find one for 15 fire damage at a vendor but when I came back it was gone :/

Anyone know where there is one?

Unfortunately item effects available in loot/shops are almost all random. Meaning, aside from unique items, there is never a guarantee of finding a certain item type anywhere.

Fire damage is a pretty common one, though. Keep checking shops and you'll find it.

There's a weapon with both Soul Trap and fire dmg in Ironbind Barrow, I believe.

This. 'Tis a unique item.

Is this unique item disenchantable? Many aren't.

This one is.

I've disenchanted it. On many toons. But not after the current patch, so if they screwed with it.... can't say yet.