musca is a fly, not a mouse...
could it be 'not even a fly was found, let alone a jar.'?
Another possibility is that olla the second time around could be ulla, as it is occasionally rendered with an o instead of a u, but this makes no sense.
The only thing we can guarantee when communicating via the internet is that we will be almost completely misunderstood, and likely cause great offence in doing so. Throw in an attempt at humour and you insure a lifelong enemy will be made.