Why am I notified about some missed calls via a text from +8888? Most of the time when there's a missed call, it shows up when I go to Phone app->Recents. Sometimes I get a text from Rogers (+8888) telling me the number and when they called. When that happens, it doesn't show up in the Phone app. 

I've got an iPhone 4, iOS 7, although this has been happening for longer than I've had iOS 7.
5 seconds with google showed me this: http://forums.crackberry.com/blackberry-pearl-flip-f85/rogers-sends-8888-text-message-every-time-someone-calls-332862/ 

Seems to be a "service" Rogers offers where they notify you if you miss a call. You need to call their customer support line and ask them to disable the "Whocalled" service on your contract.