Thanks for the timeline, truckensafely. I'll add it to the next edition of the spreadsheet. I thought the USCIS website would have the opening hours for the Seattle Field Office but no dice. Did a couple of Google searches, too, and came up with nothing so can't help you with your question. Sorry.
For general information, I thought I'd try diktus's approach to establishing my case status, since it has never showed up online. My experience was not as good as diktus's but in the end it was OK.
First off, I ended up in "automated-menu-hell" with no possible way of getting a person on the line - twice! I forget the exact menu numbers I pressed but they were the logical ones for finding out my case status. I thus called the NCS number a third time and tried a different set of menu options (the ones for reporting a change of address) that in the end got me to a first-level support person who was polite, helpful and competent. I explained the situation to him: when checking my case status online, I have consistently got a message to the effect that the case status retrieval failed and my case number cannot be found in the system at this time. He checked his own system and confirmed that he could not find it either and that his instructions for this situation were to transfer the call to a second-level support person. So far, so good.
The second-level support person picked up a few seconds later but seemed harried and just not very friendly. She also spoke - apologies in advance for this: no other nice way to put it - the deepest pure ebonics I have ever heard and even for a near-native North-American English speaker like me, she was a little hard to understand. She barely listened to my brief explanation of the problem before saying that N-400 applications were not registered on the online system and wanted to end the call right there. Given the number of people on this thread who seem to be able to check their application status online, her answer was clearly BS. I managed to gently suggest that perhaps she could check my case status for me since I knew of someone that had had that done last week. She proceeded to do that and confirmed that I had cleared the various checks and was in the line for an ID.
Again, she was trying to get me off the call by the tone of her voice but I pressed my luck and asked whether she could tell me the date I had "got in line". She effectively said no, and when I politely asked the same question in a different way, citing diktus's experience, she basically said no again. At this point, I decided that I had got the principal information I was after and that it was not worth the evident hassle of pressing on, so I thanked her and signed off.
So, the lessons of this for all of us are
1. The online case status system clearly has deficiencies, so don't panic if your case does not show up on it, or if you don't see touches.
2. It is possible to confirm one's case status via the USCIS NCS 800 number but beware the automated menu system. Following the logical sequence to check one's case status got me nowhere. Pressing a lot of zeros, which is often a good way to get a person on the line, did not work either. However, using the menu options for an address change seems to do the trick.
Good luck out there!
--J--