Hi,
As per the Pirate Familiars blog on the Paizo site (
http://paizo.com/paizo/blog/v5748dyo5ldc5) the Mongoose should be an available familiar (based on the Weasel) for PFS and general use. However it is now missing, i.e. it is no longer listed in the familiars list. This familiar is not listed anywhere but the blog and now possibly Ultimate Wilderness (don't have it yet to be sure).
Please see about restoring this familiar and verify that all from the blog are still available.
Thanks.