That's plausible. But it also could be a good guess. Lots of messages from valentines day gives us a good hint that we have a time capsule from february. Machine with time capsule reboots and then sends everything is plausible for SMS systems (smtp too).

No strong carrier affiliation for senders or receivers suggests an intermediary. Not a lot of those in the US; Syniverse, maybe SAP (Sybase 365); I don't think Bandwidth does intercarrier work.