That is entirely possible- but it could have also been
1 day lag: lacto (strain that produces CO2)
1 week lag: a wild yeast- sac or brett (or other?)
Personally, I'd make a second starter that had ~10IBU's of hop power in it (a little diffucult to calculate on a smaller starter scale)-...
If you could keep the bottles from breaking, you could take them down to absolute zero and the bugs would be fine once you warmed them back up. It's excessive heat that kills.