Possible Clues:

• Texter's valediction
• 'Bye for now,' in a text
• Texter’s “ta-ta!”
• "Until next time," in instant messages
• 'Chat soon,' in texts
• Latter-day signoff
• 'Toodle-oo,' in textspeak
• "Until next time," in IMs
• 'gtg but c u soon'
• Texted ''ta ta''