You need to report this incident to the police as well if you have not done so already. Give as much info to them as you can such as the day, date and times of the incident. Tell them where it happened. Give them as much device info as you can such as the last known location of the device, IMEI number and proof of purchase.
If you can, describe the person - what did they look like (hair colour/style/ft or thin, eye colour, tattoos or piercings, what were they wearing - clothes, jewellery, glasses,
Phone the local police station to find out if it has been handed in.
Also look on Buy and sell groups as well as lost and found, for your area on Facebook and anywhere else that these types of groups exist