NOT sending messages?

I'm not sure if my phone sent the last two texts. It is sending them to all my contacts except one. It is unlike this person not to respond, especially after several hours. Also this person had sent me texts and I can receive them but they are unrelated to the messages I sent them. Bottom line: I don't think my Droid is sending messages to this one contact.
*this particular contact has (and is the only contact with) 200 messages in the thread. I don't know if that has anything to do with it.
*it says that the messages have been sent under the text


Sent from my SCH-M828C using DroidForums

Can you call them to verify whether they're being received or not? It's hard to troubleshoot an issue when you're not sure whether it's truly an issue.