The TSA largely looks for physical evidence that a passenger could be a threat, so they'll generally have no reason to search through the data on your phone. After all, they're the Transportation Security Agency, not a detective agency. Even if they did have reason to want to access your phone, they'd need a warrant.

While it is rare for security to "take" your phone in a permanent sense, agents may briefly handle or request to inspect your device for several critical safety reasons. First, the TSA and international security agencies may ask you to power on your phone to prove it is a functional electronic device and not a "dummy" casing used to hide explosives or prohibited items. If a phone is dead and won't turn on, you might be denied boarding or required to undergo additional screening. Second, security officers often swab the surface of mobile devices for explosive trace detection (ETD); because phones are handled constantly, they are prime candidates for picking up microscopic residues of banned substances. Finally, at international borders, Customs and Border Protection (CBP) officers have the legal authority to conduct a "border search" of electronic devices to look for evidence of illegal activity or digital contraband. While this only happens to a tiny fraction of travelers, it is a standard part of their mandate to ensure national security and prevent the movement of illicit materials.