Welcome.
Unfortunately, some restaurants do black out certain dates/times - usually Fri/Sat. There are even a few that still require you to make an actual reservation through iDine to get the miles. On the plus side, most (though by no means all) restaurants have waived the former iDine policy of one-visit-per-month-per-airline.
The way to get around the weekend blackouts is to purchase a gift certificate during the week. Idine has always considered the date of purchase to be to be the "date of transaction".
As you are new, here is some advice that should serve you well:
Check online to be sure your restaurant is still participating before you go. I had one instance where the rep was willing to give me credit as it had only been a few days since they'd pulled out. I've also had a rep decline credit for a March visit for a restaurant that ended points on Jan. 31st. It would be nice if iDine could give at least a 30-day warning online of impending departure; they seem to be able to tell us of new joints before they are actually available for credit, so only fair to work both ways.
SAVE YOUR RECEIPTS! If there is a glitch of some sort, you will need to send a copy to Idine for them to give you retroactive credit (appearing online as "manual tickets"). One of the few times a restaurant did not give me a customer copy, their credit didn't go through. I had to send an edited copy of my credit card statement, which was a pain.
Credit posts online @ iDine within 5 [calendar, not business] days of transaction in virtually all cases. If there's nothing showing a week later, call iDine to set up an inquiry.
It's a good program - esp if one travels a fair amount. The reps are polite, friendly and helpful. And the miles are free to the diner!!
P.S. I do feel your pain as Seattle is heavily blacked out on weekends, too.