I couldn't find an authoritative reference to state that a snake wouldn't do that. The main climbing snake in Texas is the Rat Snake. While one of those could climb into your hammock to cuddle, I doubt they would. At the end of the day it is much easier for a snake to slither into a sleeping bag/tent/boot/etc. than a hammock. Those items are all on the ground, and therefore easily encounter-able. It would have to be a pretty smart and determined snake to slither along the ground, sense your body heat above them, climb the tree, slackline the hammock's webbing just to cuddle. Given that and what ShemSeger said in the comments:
Hammocks are typically what you sleep in to avoid snakes.
Overall I think you're safe in your hammock, but if your buddies see this post expect to have a rubber snake slipped into your hammock next camping trip.