Ideally play it safe and have it re-issued. Strongly advise against stapling it back. Gluing it back would probably be acceptable/not noticeable in most cases, however stapling it could potentially damage some of the security features and marking on the visa, not to mention, raise the suspicion of tampering.
If gluing, moving it to a different page is a no no. Many visas now have security numbers/alphabets at the bottom.
You never know if some of those numbers reference the page to which the visa was affixed and thereby invalidating it if moved.
Finally, doing anything to the visa/passport could be at the extreme be interpreted as mutilation which invalidates the whole passport and require replacement using the US Department of State guidance as a example.
If your passport has been significantly damaged, especially the book
cover or the page displaying your personal data and photo, you will
need to apply for a new passport. Damage that might require you to
replace your passport includes water damage, a significant tear,
unofficial markings on the data page, missing visa pages (torn out), a
hole punch, or other injuries.