Possible Clues:

• IM sign-off
• 'Gotta run,' in a text
• 'Toodle-oo,' in textspeak
• Texter's bye-bye
• 'lol, peace'
• Texter's valediction
• IM signoff
• 'Bye for now,' in a text
• Texter’s “ta-ta!”
• 'Chat soon,' in texts