Possible Clues:

• Texting ta-ta
• "Until next time," in IMs
• What best-selling 2004 young adult novel was written entirely in the form of instant messages?
• Short 'goodbye'
• 'Bye for now,' in textspeak
• Closing letters
• 'gtg but c u soon'
• B4N alternative
• Texter's sign off
• 'Bye for now' in a text