I've occasionally had things crash in ways that have swallowed ctrl-c. More recently I've learned to still try ctrl-z in those cases, as that often still works (but not always).
None of this is very common, but I found myself opening another terminal and killing the ssh process probably tens of times before I learned about the ~ escapes.
None of this is very common, but I found myself opening another terminal and killing the ssh process probably tens of times before I learned about the ~ escapes.