Beeches cannot tolerate standing water for any length of time. If this is indeed, what has happened, you could try moving it immediately to a drier spot and see if it has the energy to releaf in the new spot. Otherwise, it is gone and you may want to try another one in the drier location.
When a plant is in standing water, the roots effectively drown and cannot participate in nutrient and water supplementation to the tree itself.

I'll probably try moving it as a desperation measure. I'm kind of irked, because the area I planted it in used to be quite dry...but now receives a lot of rain runoff due to landscaping work on my neighbor's property.

The only good news is that you now have an oppurtunity for a new tree that loves moisture!

Say hello to Taxodium distichum 'Shawnee Brave'!

Shawnee Brave looks pretty tempting, but I think it would get too wide for the available space. I originally picked Dawyck Gold (in part) for its extreme fastigate habit.

Are there any other tight fastigate trees out there that don't mind getting their feet wet?

Regal Prince Oak...but that might be too wide yet in time.