Lost Necklace on Malahide to Dublin Pearse Train

I lost a necklace on a mainline train which left Malahide at 7:30am (the delayed 7:06 from Drogheda)on Thursday 13th January and arrived into Pearse station at 8am. The necklace is a tear-drop shaped diamond with two smaller circular diamonds above it, on a thin silver chain. The necklace is of great sentimental value and its return or any information about it would be greatly appreciated.