I think I understand the problem you're having - it sounds like you have a default app set for opening .txt files. If you pull down the top menu More->Applications->Installed Applications select your note app. Scroll down to "Launch by default." From there you can press Clear Defaults. Do this for all your note apps or whatever you suspect is opening your .txt file. Now when you click your .txt file you should be given a choice of what you want to use to open it - don't check the "Use by default for this action" box and you should be able to test out your different apps and keep track of which is which. You can then set your default app once you've made your decision if you want to.
Hope this helps.