Gap in logic

Hi EnglishForward,

I'm an EFL teacher with an unusual question. I have asked some of my collegues, to no effect, so I thought I'd post here for some ideas if possible.

We've been discussing a letter that we received from a company, who made an error with an order that we made. Their response included:

"as far as we can tell..." blah blah blah and "because this is the case"

Now, to me, there is a massive gap in logic between those two sentences. "Because" implies there is evidence. "As far as we can tell" implies they have no substantial evidence.

My question: how do I explain this lack of logical reasoning. Is there a special way (or phrase) to describe a conclusion that has been made using a break in logic?

Many thanks

Andy