I don't know the bionic's software. I suggest looking in the message app's settings, see whether you can increase the number of messages it displays.
One thing though: I've not myself met an app that limits the length of history it shows. I have however met apps with an option to only keep a certain maximum number of messages per thread, and if your one is like that it may have deleted the message for you. I hope not, but it's possible.
If you can't find such a setting, try installing a third party messaging app, such as Handcent or Chomp, and see whether they show the message. These apps all use the same message database, so if the message is still in there you should be able to see it using one of these.
Hope this helps, and good luck.