Hi Jen,
The reason your textfield is jumping back to the original position is probably because you have also selected the X, Y and Z-position when you created your Keyframes.
When you're creating keyframes, the key is to only select the values that you need. In this case, only the Alpha and you should uncheck everything else. Otherwise these values will also be saved in the keyframe. To make sure these values are not saved, click on the words "Position", "Scale" and "Rotation" until they turn red. Then these values won't be saved along.
See if that works for you?
Good luck,
Kenneth
#XPression