Touch an Iceberg

As I walked on a busy stretch of road near King's Cross, I noticed this small card stuck to a lamp post:

I looked around for numbers 20 or 22 in what I assume must be a series, but this was the only card I could find. Sadly, I did find another ghost bike nearby:

I don't know when this bike was placed here, but it was on a road on which I travel by bus on a regular basis, and today was the first time I saw it. Unfortunately, it didn't last long, and one day in early January when I went by on the bus, I noticed it was gone.