Hi @gulluwing
Thanks for posting about this. The easiest way to address this is to sign into Strava on the web and go to Training>My Activities from your dashboard: strava.com/athlete/training
From there, you can filter your activities by "ride" and then by "bike" so you can see which rides do already have a bike associated with them. I would recommend opening two browser windows side by side - in one of the windows filter by bike, and in the other one display all your rides. You should be able to pick out the rides with no bike attached, although if you have more than one bike on your Strava account you'll need to do this process more than once.
Once you've identified the rides without a bike attached, you can edit them (this will need to be done one by one) and add the bike. You can enter the edit screen directly from the strava.com/athlete/training page.
How to Manage Gear on your Strava Account
I hope that's helpful and let us know if you have any more questions about this.