`memcached_set` returns `MEMCACHED_NOTFOUND`

[MaoZiming]

I am getting weird memcached_return_t (MEMCACHED_NOTFOUND) after calling memcached_set.
If I understand it correctly, MEMCACHED_NOTFOUND should only apply to memcached_get.
Do you know what kind of situations where memcached_set could return MEMCACHED_NOTFOUND?

[m6w6]

You need to provide reproducing examples, please.
And some versions, like library and server version.