The 29-year-old was on his brother Eamonn’s stag weekend in Hamburg when he vanished in the early hours of February 10.
Friends and relatives last saw him in the Veermaster Bar after which he was identified on CCTV footage from the Baumwall area.
Searchers have now received an unconfirmed reported sighting of him in Harsefeld, about 30 miles away.
A statement released on social media said: “As many of you will be aware, a sighting of Liam was reported in Harsefeld, a town 50km west of Hamburg.
“Unfortunately, due to the lack of CCTV and photographic evidence, it was not possible to verify this sighting. Therefore, we are still uncertain as to Liam’s whereabouts.
“We believe it may be possible that Liam has left Hamburg. We therefore ask that everyone shares this page with all friends and family throughout Germany.
“We also ask for volunteers to print our latest poster and put some up in their local area, wherever that may be in Germany.
“Although it is possible Liam is no longer in Hamburg, we do not have evidence to suggest this.
“We therefore ask everyone to remain vigilant in Hamburg and the surrounding areas. If you think you see Liam, please take a photo and approach him. He speaks only English with a Scottish accent.”