Billboards are printed on single sheets of banner material and then affixed to their bases with stretching cords across the back. Usually if you look, you can see someplace where the "face" is folded over in part of the mounting process.

On the picture of the actual board, you can see two such places at the top on each side, circled in red. Note that while the one on the left could be hidden by the angle, the one on the right would have been even more visible than it is.

Also note the imperfection across the entire bottom of the image. It's nowhere to be seen on the enhanced board.

Also note that since billboards are heavy material folded over itself at the corners in the hanging process, their corners are never going to be the pixel-perfect 90 degree angles you see in the enhanced version.

Then look at the color: Two different cameras and days and conditions, true, but note how flat and lifeless the real board is in comparison with the enhanced one. And, also note the yellow. Many grand-format printers are inexpertly profiled with a particular brand of profiling software that will leave a definitive blue "scum dot" in solid yellow areas. Which is exactly what you see here.

Finally look at two zoomed-in sections of the same area of the board. In one, the black has no detail at all, the black has a different cast, and again, the line that stretches across the bottom of the board is not there.

If there are bets riding on whether the board exists, that's one thing; but if the bets are on whether the photo posted yesterday is fake...it is.