A lost string means:
- Torn string and not replaced
- Lost string during transport without bow case (or simply lost)
- the string is worn out, although the bow was shot very little...
- the string does not match the colour of the bow
- "someone" tied knots in the string to shorten it
- the string never fitted to the bow and the owner did not know how to make a new one
- the string was just "shit."
- the seller has no idea about archery
and all other reasons you can think of
P.S. I haven't lost a string yet either, but I have seen many bows without string offered for sale. But better without string, than for example if the string is pulled the wrong way on a recurve or the string was never relaxed...