It's said to have happened on Sidwell Street on Monday 15 July.
A woman was approached by another woman who took her phone and then punched in the nose at around 11pm.
Officers have issued a picture of a woman they wish to speak to as part of their investigation.
City lose at home again
Kyle Wooton brace gives Stockport win over sorry Exeter
Calls for inclusion on Plymouth lord mayor role
It traditionally alternates between Conservative and Labour
Upgrades to Plymouth storm overflows to take place
Hoe bathing waters are priority to stop sewage discharges
Dartmoor finances facing biggest cut for years
'Do DEFRA think the Dartmoor pixie exists?'
Rare curlews and martens are leaving Dartmoor - for now
'We hope some of them choose to come back to the wonderful place that is Dartmoor'
Dartmoor phone mast gets the go-ahead
Better broadband and emergency cover promised
