I Am sorry that the OP was caught up in this particular situation. Yet, the one glaring fact that some posters here have overlooked is, that a passenger on his flight had made the allegations and TSA/HLS/FBI and whoever else had to follow up.
I would be pissed too, but to open your phone to look at pictures texted by friends while in such a public space would conjure the wild imagination of those who do not know or understand human dynamics and interaction.
Then again, if the OP was a human trafficker, then Law Enforcement would be remiss in terms of not investigating fully and a black eye.
Often, we read about similar situations happening such as the time when a Nobel Prize winner was working on some equations during his flight to SFO and was arrested at the airport because a fellow passenger did not understand equations or what he was working on and thought that it was in Arabic and needed to be addressed ASAP.
This fits right in this category or so I believe.
I trust the OP will have less eventful flights going forward...
Safe travels to all.