No. Once text has been converted to outlines the operation can not be reversed.
If you need text back, your only choice is to delete and recreate text.
This holds true for all Adobe apps once text has been converted to outlines.
You must need a vector shape/ object to create mask in XD.
In first example rectangle is what masking the fruit image.
But In second case there is no shape to mask the cat.
A picture itself is not a mask! You have to have a vector shape/ object to mask an image, otherwise it simply won’t happen.
And If you think you will include/incorporate an image into ...
You could use Inkscape which is free, or virtually any vector image editor.
Copy and paste your signature image into Inkscape, lock it in place. Then draw the signature paths on top using the Bézier Tool (aka Pen Tool). Once you have finished unlock and delete the image.