What exactly does "downloaded pictures from text" mean? You mean an image from an MMS, or some other sort of message, or a text that included a link to a picture hosted somewhere else (in which case what did you use to download it)? Can you view the image in your message app?
If it's been downloaded why can't your regular gallery app see it? Might it be that it hasn't actually been downloaded (or is stored in the message app's internal data or cache, as something like FB Messenger will do, where your gallery app can't see it)?