Before I start, I appologize in advance for the long post. Well, my dad and I have been turkey hunting for three seasons (including this one). We've yet been able to get a bird, mostly due to where we were hunting. This year we joined a club and had high expectations. Unfortunately, the first two weeks they were all henned up and wouldn't make any noise off the roost. We only get to hunt on Saturdays, so that just makes it harder. Well today we almost got our first birds. Someone was in the spot we were hunting the first two weeks so we had to go somewhere else (blessing in disquise).
A large chunk of the property is clear cut with powerlines going through them. If you walk far enough down one of the power line lanes, it's woods on both sides with bright green grass in the middle and a small river running through the grass perpendicular to the power lines. By the time we got to this spot, the sun was completely up. Well before we could even call, we heard a gobble off to our right in the woods. We waited a bit and heard about 3 or 4 different gobblers.
So we set the dekes up and found some good tress right on the edge of the woods opposite the side we heard the gobbles. We started calling and they answered. They didn't gobble much, but each time the gobble was closer. After about 20 minutes, we heard a LOUD gobble just on the inside of the trees across from us. I was thinking, "This is finally it. We're gonna do it. About that time, my dad, who was sitting about 15 ft away from me and had a different view, said, "Here they come." I couldn't see them, but he said that he could just see 5 or 6 red heads bobbing right above the brush line. About this time, they starting making this pucking sound. It was really deep pitch, which surprised me b/c I had never heard a hen with that deep of a pitch. Dad said that they were walking left and right making this pucking sound.
After a minute or two of them doing this, they just turned around and walked back into the woods. I only ever saw two of their bodies as they turned around to go deeper into the woods. After it was clear they weren't coming back, we got up and walked to each other and talked about it. We were both upset, but we were excited too b/c that was the closest we've come to bagging one. It would have been nice for both of us to get our first ones on the same hunt. Anyways, we thought they may have not liked our deke setup and just left. Well we went into the woods where they came from and it turned out there was about a three foot wide shallow creek running down through there. Apparently, they came to the creek and didn't know what to do about it and just left. Since we had never hunted this spot, we didn't know it was there. Now that we know it's there and there are birds there, we'll be heading back next week and hopefully finally get our first birds.

A few things.. If it was public land, theirs a small chance they were scared by the decoys.. slim chance, but could happen.. Secondly like you said, they may have got to the creek and said screw it, im not gonna cross the creek to get over there..
The only thing that has me wonering is this "pucking" sound they were making.. to me it sounds like they were alarm putting.. and this is most likely because they didn't like something about the setup... maybe when they got close they saw you or your dad move.. this will usually put birds into a half alert.. and they will putt likeyou said you heard... To me, I would say the reason they got up and left was the third reason.. they saw something they didnt like and it spooked them a bit, so they went the other way...