How do you explain the thread sticking to an ice-cube when salt is sprinkled over it?
I conjecture that there are several things happening.


Step 3:  Addition of salt will melt the ice at its immediate point of contact. The string will naturally be surrounded by the highly concentrated brine (salt water).
Step 4:  This is enough time for the brine to get diluted, noting that there is an infinite reservoir of potential water by way of the ice cube.
Step 5:  Once the salt gets sufficiently diluted, then the comparatively large ice cube provides the necessary cold for the (now) very dilute salt water to reform as ice.  


Recalling that in Step 3 the salt water surrounded the string, then ice naturally forms around the string in Step 5, hence you can pick up the ice cube with the string.