Looks like Windows Mobile is saving it's last secret status for the unlock code. I recently got onto a Windows Mobile Smartphone (Vodafone) and opened the Facebook app on it. When I went to look at the home screen, I was surprised to see a "Forgot password" text across it. Looks like Spark isn't just saving the password, but is also restoring it to make sure that user is still logged on the phone and therefore still able to use it. Or perhaps it just changes "ON Phone" status to other when it gets a special "signal" from somewhere that it cannot get in the locked state.
When I disabled spark this happened, and I could not figure out why - my Spark didn't seem to have this feature enabled by default. Anyway, I enabled spark again and went into some groups (gathered through Spark); my Spark didn't recognise me, so I just started typing random letters and numbers. Finally, after about 10 minutes of getting nothing I thought I might just need to restart my phone and check again... no luck there either. Then I realised that the problem was with the IM client software on the Spark. Since I'm used to connecting with my Spark through WAP I had never encountered any problems, but it turns out that my IM client software is broken on this platform, forcing Spark to use a regular IM client to connect with me (which it does).
Luckily spark has an uninstall option in the settings and this was what I used to uninstall it again. Once this was done my IM experience was back again. So, if you want to try out your IM software on your Spark again and see if it fixes it; go into the "Phone" settings, click "Fuel" and enable "Unlock Screen." This will allow you to use your Spark without having to connect it to a computer - great if you're out and about! To be honest, my experience with Spark was poor on the first day; I'm now a lot more comfortable connecting to my IM clients through my iPhone, so hopefully these problems will go away on subsequent days.