Possible Clues:

• "I guess that's that!"
• Slangy lead-in to "What can you do?"
• "I guess that's that"
• Lead-in to some bad news
• " ... or not"
• "Alas," informally
• 'So much for that!'
• Modern slang for "Alas ..."
• 'Eh, what can you do?!'
• 'So, that's disappointing,' online