How can I find out another person's web traffic numbers?

I have lient which I suspect has been scammed by a blogging website. Stating that they receive 365,000 view per month. My client paid a lot of money for an ad Blog post with a link back to their website.

The woner of the blog claimed the post had like 12,000 views and they received 765 clicks.
My client didn't receive 765 clicks in their google analytics feedback, they only received a total of 7 referrals from that website and their sessions didn't increase or the number of users didn't increase etc.

Is there a way for me to:
1. Find out if they did recieve these clicks?
2. Find out how much traffic this bloggers website actually gets?

Check their Alexa rank? If they're not in top 1,000,000 then 365k views per month is bullshit.

Analyse the blog. There post quality and off course Alexa rank of that blog.

You will get idea from there.

You can ask your client to provide read only access to Analytics of his website, so that you can check whether they are receiving traffic or not.

Did your client include a image in the post? If the image is sourced from your client's server you can count how many times the post was seen.

Analyze them on semrush, check how many top ten rankings they got.