Is it just with Verizon? Which rom are you using? Have you tried going back to the standard sprint rom? which apps are you running?
I had that happen to me with S2U2 when I first started playing with it. It turned out I needed the ResetUnreadCount.cab because many times when it would sleep, i would watch it wake up at the point of which the SMS text messages should've been received but there was no notification and the texts just disappeared.
Try sending yourself some texts first from your own phone and then because you're with sprint like myself, go here http://sprint.zipwhip.com/
and send yourself some texts, even some timed texts. I received them almost instantaneously. If you get a delay, it shouldn't be for very long.
If you still have the problem go to a service center and tell them its something wrong with you phone on the network. I had a really bad problem with my Sprint Mogul / Titan and missing texts and phone calls. The techs could never figure it out, which is why i'm using a touch pro 2 (actually I had the same problem with 3 back to back replacement moguls, I'm guessing the model itself was just having problems on the network, but I doubt that for the touch pro2).
Hope this helps