Is there a term for when a component desolders itself from the circuit?
Systems that have been known to experience this kind of failure mode (for example the early XBox-360 consoles) probably have some kind of deliberate thermal dissipation system (heat pipes, heat sinks etc) that have failed for some non-electronics related reason.

In the case of the XBox-360, some units failed because the GPU cooling was insufficient to prevent overheating, in conjunction with mechanical provisions not being strong enough to stop the SMD chips from sliding across the board once the solder melted.  Subsequent builds of the console featured upgrades to the mechanical fixings and to the active cooling components.

I think it is unlikely that there is a serious phrase that succinctly describes a generic desoldering event in mundane electronics.

Such things are system-level engineering failures.