
Nice find! That's the way to pick up salvaged wood. Good for them, better for you.
Yep, sometimes when I hit a wood pile that has more than just pallets, I will bring along a cordless circular saw, a reciprocating saw, some hammers and a crow bar. I don't need them very often, but when you don't have them to use, you sometimes lose out on some good salvage wood to the next person with a larger trailer or tools to cut the wood to size.
Oh yeah, I also have extra rope and tie downs in case something needs to be secured to the trailer, like over long wood or over wide stuff that I can find. I picked up some 12 foot long beams one time and had to tie them down in my 8-foot long trailer to safely get them home.
IIRC, I used 2 of those long beams to make a grazing frame for the chickens inside the chicken run. Good use of those salvaged beams as they were not high-quality wood, but perfect for my grazing frame project.
Those shorter pieces always come in handy for something. I keep them all and eventually find a good use for them. I have my cut-offs in a bin, stored vertically, so I can quickly pick out a board for the length I need. That works pretty good for me.

I don't think I have ever seen a 4X12 beam. I bet they are pretty heavy. Any idea what you would use them for? I know I'd pick them up and bring them home, even if I did not have a clue at the time what I would do with them. Sometimes having those pieces of wood in the shop will talk to you and suggest a good project.