Why did this happen?

[guesswho]

As I was walking back to the truck, I heard 3 toms gobble about 125 yards from me. 

so I decided to sneak to a tree and set up.  I know they could not see me or hear me.  After I called, they never made another sound.

Never under estimate their eyes or ears.  125 yards is nothing in his world. 

It may be as simple as they heard you walking to the truck and they gobbled.   They could have been easing towards that walking sound about the time you were sneaking to a tree, and I'm guessing there were two of you.   A number of things could have happened, but I'd guess they at least heard you and possibly even seen you.