How to download my iPhone's lock-screen wallpaper?

In October, I visited my grandfather, and my family photographed the two of us on my iPhone 4S(unfortunately for the last time since he passed away in April). Shortly afterward, I set our picture as my lock screen wallpaper.

Around New Years Day, my computer (which contained the pictures from my iPhone 4S) crashed, and I lost access to some Photo content from iCloud. Despite this loss of the photos, my wallpaper picture remained (but not in the photos section. It only remains as my lock-screen wallpaper, and I can't access or download it anywhere).

In an optimistic and defiant stand, I never changed my iPhone lock-screen wallpaper thereafter and hoped I would eventually discover how to download it onto my computer or find it somewhere on the iPhone 4S where I could upload it to MediaFire or someplace where I could access it from my computer… Or anywhere other than my lock-screen?

How can I access this photo? It does not appear in my Photos with or without iCloud. (I relocated most of my photos including this one to my computer and deleted it from iCloud to save space. It only exists in my inaccessible computer (RIP) and as my iPhone 4s lock-screen.

Sorry for your loss but screen lock and wallpaper photos have to come from some access point the phone can touch e.g. Photos section of the phone. Due to the PC loss, I'm afraid there's no way to replicate that as an option. Someone else in your family have a version of the photo they can scan/email to you? That's possible the best solution. Best luck.