The way my Sony HDTV receiver works, it only reads the PSIP during the initial scan, and then caches the entire thing... so if it worked the first time, it will continue to work until I scan again. On the other hand, if it didn't work the first time then it won't start working right until I scan again (which as been somewhat of a pain with channels like CFTO that had some trouble with their PSIP going in and out), and it never knows about new subchannels or other station changes until I scan again.

On my older Samsung tuner, it would "auto add" HD channels as you found them (meaning it cached the virtual channel), but it would re-check the PSIP each time for changes or updates.

If a tuner doesn't know about a channel then you'll have to tune in the "real" frequency; it sounds like there's something invalid about the Global PSIP that's stopping the Sharp from saving the virtual channel information for later usage.