As you know I have a pet peeve about things being linked incorrectly on Pinterest. Here are a few ways that I have been able to find missing links while pinning to my boards.
As I mentioned before I don't repin from the thumbnail pins, but open each one in a separate tab first. To do this you right click on the pin and choose "Open in new tab". Or if your mouse has a scrolling wheel, you can use it to click on the pin and a new tab automatically opens.
Once all the tabs are open I then check each one by hovering over to see what it is linked to - the URL will pop up just above your task bar. (Actually if Pinterest would make it possible to see the source link in the thumbnail view that would be great!) In some cases it's obvious if the link is the correct one: if it's not clear then I click on the pin which automatically opens the source site.
On a blog I need to search for the exact post the image came from. Sometimes I get lucky and it's right on the front page. Other times not so much. If it has been linked to page 6 or sometimes 45 then I go backwards through the blog archives until I find the post (most blogs will provide a link for getting to the older posts). If that doesn't work then I check to see if the blog has a search function and type in the keyword. Say it's a recipe for lemon garlic chicken, then I type "lemon garlic chicken" in the search field. If this starts taking too long then I just give up.
Another method that works sometimes is to do a google search for the image. I'll type in the keyword and then choose "image" on the google page. One of the results you'll get will no doubt be the image on Pinterest, but lots of times you will find other instances of the image and then you can check to see if they are linked to the original source.
I've also given up pinning anything that comes from Tumblr. That place is like the black hole for links! (And to think I loved it so. Ah youth.) Things get reblogged so many times and links get lost, so when I see an image linked from Tumblr and it has like 14, 367 notes over there I don't have much hope in finding the original source. One day I almost fell out my chair laughing when I clicked on a pin that took me to a Tumblr blog and the source on the Tumblr blog was a pin on Pinterest (which wasn't linked properly)!
Once I've found the original source I copy the URL, then repin the image, and in the pop up window that appears I choose "See it now". At that point I can edit my pin and change the source link.
It's a kind of long process, but I only do this with things I really love. If it's just a cute or funny picture, or a craft that's an "eh, maybe", and it's taking too long to find the source, I just give up and move on. In a way it means I am only pinning the things I really truly love. Ok maybe not 100% but that's what I tell myself!
I hope this helps in some way! And if you have found another way to do this, or have any other tips do share. I'm always looking for ways to make the pinning experience simpler.
Don't forget to link with love!