Losing contact in an email back-and-forth is embarrassing. Especially when you don't actually know the person and you start off very keen, but then die off.
This has happened to me with a contact I made serendipitously via another contact in New Zealand. I don't even really know the NZ contact. We've met once years ago at a modelling workshop. She is a pharmaceutical researcher and was trying to get some models built for what, in my opinion anyway, is a simple diffusion across a membrane issue. I think she agreed, but the rest of our group was hell bent on some differential equation based nonsense that was clearly inappropriate for something that was clearly a spatiotemporal process! Anyway, that common ground left us as occasional emailers to each other. This year I hope to visit her in NZ - probably in June.
Anyway, she introduced me to another research - a material scientist who constructs drug delivery devices - from Northern Ireland. I am really interested to work with this guy because he is interested in similar things to above, but also because he actually understands applied mathematics, probably better than me too.
I contacted him late last year and we tried to set up a phone meeting (who uses the phone anymore? honestly!)...but various things got in the way: winter storms in Belfast, Brisbane floods, then my holidays and numerous overseas trips.
I looked in my email and noticed his last email to me was February 8 - 3 months ago!!! I hastened to send a reply this morning in order to reestablish contact and set up a phone call for this coming week. Hopefully he hasn't lost interest :-)