Paul Pogonyshev <pogonyshev@gmail.com> writes:

> Git commit fd1ee05977.
>
> Open any file with TRAMP. From this buffer, evaluate:
>
>     (let ((file buffer-file-name)) (with-temp-buffer (insert-file-contents file nil)))
>
> This works fine. However, if you use a region:
>
>     (let ((file buffer-file-name)) (with-temp-buffer (insert-file-contents file nil 1 10)))
>
> this fails with an obviously wrong (file is certainly there) signal:
>
>     Debugger entered--Lisp error: (file-missing "/ssh:...")
>       signal(file-missing ("/ssh:..."))

I tried this recipe with the current trunk, and things worked fine for
me.

Is it possible that you have an old version of tramp somewhere in your
load path?  I seem to vaguely recall that insert-file-contents +
start/end was something that was fixed sometime last year.