According to Asian E-News Portal, a fan from Asia saw him and they took a photo together.
On Weibo, Nicholas's fan uploaded their photo and disclosed he was filming an advertisement:
"Nicholas comes to Lisbon to film an advertisement and shopped around.
"I felt very fortunate to take a photo with a celebrity.
"Hope everything will run smoothly for Nicholas Tse in Lisbon!"
This picture appeared amid rumours that Nicholas and Faye would be married soon, which explains why fans were puzzled after seeing the photo.
Those who hope the celebrities will stay together can breathe a sigh of relief.
Take a look at the gallery below to see more images of Nicholas Tse and Faye Wong.