The trap would not have even made a mark on your boot. People think that traps cut off legs and break fingers and such, it's just not true. I've caught my fingers many times and I'll admit, it hurts a bit. But that is it. If you step in someones leghold trap it will just snap harmlessly under your boot. Unless bear traps with over 10 inches of jaw spread are legal to use on land in Oregon. I highly doubt it, but I don't know for sure. In WV, you can't have a trap on land with more than a 6 inch jaw spread. Nobody can get their foot in there, and if they did, it wouldn't cause any harm.
I've caught numerous pets, they are fine. I've caught my own pets many times, not even a limp. The trap will close on the animals foot and hold it there.
As far as signs, I have used them in areas I know the rabbit hunters are out in force. Again, my traps will not hurt their dogs but can be an inconveniance for someone who does not know how to open the trap. So I put out a sign so that they can hunt somewhere else if they are worried about it.
Make sure you study alot prior to setting traps. You are a long long way from being ready to put steel in the woods. I don't mean this in a bad way, I'm being serious. Learn all the regulations, go with an experienced trapper, buy some videos, search the archives. Knowledge is key