You could probably do it with timing tricks related to video refresh. Wait until the monitor has finished refreshing, then draw the text into the framebuffer. Leave the text there a short while, but erase it before the monitor starts refreshing again. Repeat.

The screenshot would have a chance of capturing the text, depending on exactly when the screenshot pulls pixel data out of the framebuffer.

This might not work on certain devices. You need access to the refreshing timing information. The capture mechanism used for screenshots might also vary.