How is Pam's Song and Shielding Scroll different?

Shield scrolls are used before scrolling. You put the shield on the item, and then you use whatever scroll you wanted. Regardless of whether the scroll fails or succeeds, the shield gets used up. You need another shield if you want to try another scroll.

Pam's Song is used after scrolling. If you attempt to scroll something and it fails (but doesn't blow up), and you have a Pam's Song in your inventory, a dialog pops up asking whether you want Pam to sing a song and restore the lost slot to the item. If you choose not to, or if your scroll succeeds, Pam's Song does not get used up.

Can both Pam's Song be used in conjunction with 1) whatever it was that saved your scroll if it failed Guardian Scrolls and 2) wards?