Please I really need help with this question!?? ( especially from girls!)?

Hello guys! Please I really need help with this question as it is driving me crazy. About 3 weeks ago I met a lovely girl on the train who was staring at me. We started talking and I really liked her. After a while, when she had to go she suggested we should keep in touch so I gave her both my phone and email and when I asked about her one she told me her phone was greek ( she is actually from Greece) but she would send me her english number soon. The problem is 3 weeks have ped and I never heard back about her since then and I can't contact her as I haven't got any info about her apart her first name and where she studies english language. What shall I do? I modestly been with many girls but somehow I really felt that one was special and I still dream about her ( I know it sounds strange as I only have seen her once, but i just feel I have no control over it).I thought about leaving a post at the board of er school, but thought better not...but then I had the idea to post an ad asking if anyone knows about this girl at her facebook english school page? Would be something very discreet...any suggestions about that? Is it a good idea? I know I sound desperately but I just can't forget her beautiful smile...Thanks!!!