Accidentally deleted files like that will require a file recovery program. If the image is worth it, do a Google search for memory card recovery programs and purchase one. Price is usually in the $15 to $35 range. Also, if you need that photo and intend to recover it then DO NOT take any more photos with that card so that the data will not be over-written until the data can be recovered.
Search for memory card recovery or canon photo recovery on Google. When choose the data recovery tools, please note:
(1) Carefully check the "file formats" it supported, make sure it support Canon Raw formats: CR2 and CRW.
(2) Do not pay for it unless it has found the lost pictures.
Tips: Save the retrieved files on the hard drive of your computer. Do not save them to the memory card of your Canon camera.
Have saved your deleted camera images on the phone internal memory or inner memory card?
If you do put them on the internal memory, without data backups stored elsewhere, you may also have no chance to take them back.
But, differently, if you do save them well on the camera memory card, even without data backups somewhere, you also can have possibilities to rescue your preferable photos back with photo recovery software.
So, do not give up ay hope and check whether your images are still recoverable.
Check this to know more:
Prepare and update camera data backups from now on.
There is no way to undelete in the camera itself.
As someone else already stated, the only way to recover an image from a memory card once it's deleted is to run an image recovery program on the memory card... as soon as possible.
DO NOT continue using the memory card for other photos. That might overwrite the image you deleted and want to try to recover. Once it's overwritten, it will no longer be possible to recover it. Also DO NOT format the memory card until after you have downloaded and recovered any images you wish to retrieve.
There is no guarantee of success trying to recover a deleted file. If you stopped using the card immediately and set it aside... the odds are a lot better. Odds are also better with an accidental deletion, than if something has corrupted the card. Worst case... a while back I had a card fail (brand new... first use!) and it was completely unrecoverable. Still, I tried! On the infrequent occasion I've needed to recover images, I've probably had about 66% or better success (not counting the completely failed card, but including a couple times when there were corrupted files on the card for various reasons).
If you need a recovery program, send me an email. I just bought some memory cards and included with each of them is a free copy of Lexar Image Rescue 5, which I've used a few times myself and have found works pretty well. Having bought four memory cards, I've got four software licenses... but only need two, at most (one for my laptop and one for my desktop computer... though I think I may already have the latest Image Rescue 5 installed on one of them).
Just as a minor side-note: "Cannon Mark II" really doesn't tell us very much. Canon has made 1D Mark II, 1Ds Mark II, 5D Mark II, 7D Mark II cameras, not to mention a number of Mark II lenses, Mark II teleconverters, Mark II flashes, even Mark II macro extension tubes.
09/26/2023: New firmware updates are available.
08/18/2023: Canon EOS R5 C training series is released.
07/31/2023: New firmware updates are available.
05/31/2023: New firmware updates are available.
05/18/2023: New firmware updates are available.
03/30/2023: New firmware updates are available.