Gmail messages disappeared from BlackBerry (Gmail account also on Outlook as IMAP)

I recently decided to change email addresses from my ISP provider's email (I use both Outlook and web-based mail) to Gmail (web-based only). I had already had Gmail on my BlackBerry for months with no problems. I tried to use Gmail's import email feature to move my emails from my ISP provider to Gmail, but it didn't work, so I set up Gmail as an IMAP account on my Outlook so that I could just copy emails from my Outlook (belonging to my ISP provider's email account) directly into Gmail. I did some of it last night, and emails past a certain date were showing on my BlackBerry's Gmail account as well. I left my Outlook open overnight to copy more folders into Gmail and this morning, while the emails show on both my Outlook Gmail account and my web-based Gmail account, all of the emails, including ones that were in my Gmail inbox on my BlackBerry before I started the email migration process, are now gone from my BlackBerry. They have just disappeared. They're not in any folders, although a handful of the emails that I moved through Outlook into Gmail are in a few folders. I'm not sure what happened. I have the account on "Forever" for "Days to Keep Messages" so I know my BlackBerry's not deleting them for that reason. Does anyone have any ideas for what I should do to fix this problem?

I should mention that I have a BlackBerry Bold 9900 and am on BlackBerry OS 7.1.0 Bundle 2108.