The 64-year-old, who has to use a stick to get about, was leaving the entrance of Homefield Park, in Homefield Road, Worthing, when he was approached by two men.
One of the men grabbed the victim’s blue Samsung Galaxy Ace mobile phone and pushed him to the ground.
Details of the incident, which happened at about 2.30pm on Saturday 20 July, have just been released by the police.
The thief was white, slim, in his early 20s and 5’8”. He had pale skin with a distinctive 1/2cm blue tattoo of a star on his right cheek and mousey brown short hair.
He was wearing a dark blue baseball cap with a black peak, a grey hooded top, tracksuit bottoms that were dirty at the knee and white trainers.
Anyone with information should call 101 quoting serial 969 of 29 July or the independent charity Crimestoppers anonymously on 0800 555111.