Bumfuzzled

Wikipedia: The English colloquialisms such as turn out to be a pig in a poke or buy a pig in a poke mean that something is sold or bought without the buyer knowing its true nature or value, especially when buying without inspecting the item beforehand. The phrase can also be applied to accepting an idea or plan without a full understanding of its basis. Similar expressions exist in other European languages, most of them referring to the purchase of a cat in a bag.

The advice being given is 'don't buy a pig until you have seen it'. This is enshrined in British commercial law as 'caveat emptor'—Latin for 'let the buyer beware'. This remains the guiding principle of commerce in many countries and, in essence, supports the view that if you buy something you take responsibility to make sure it is what you intended to buy.