A Lincoln man sustained bruising to his face when he was robbed of this phone at about 9.50pm on Tuesday February 21.
The 22-year-old man was walking along Waterside North, towards Stamp End, when he walked past a group of four people.
One of the group punched him in the face, causing him to drop his mobile phone on the floor. The offender then picked up the phone and walked off with it.
The victim followed him and the offender turned to him and demanded money. The victim told him he had no money and the offender walked off with the phone in the direction of Broadgate.
The offender is described as a white man, aged about 50, of chubby build and with facial hair.
Also in the group were a white woman, aged about 30, wearing a beige knitted dress, and another man and woman, both wearing black.
Anyone who was in the area at the time and who witnessed the incident or who saw the group of people described is asked to contact Lincolnshire Police on 101.