Please don't let this one bad experience turn you away from mystery shopping. Thank goodness it turned out well in the long run. I also received a check in the mail for $1350, a similar scenario, and just for kicks, called the phone number, and left a message for them to call me back about some lovely swampland in Florida that I'd like to sell to them - and going at a steal for just $1.35 million. Strangely enough, they didn't call back! The legit companies never send you money to do a shop, and certainly not thousands of dollars!!
I've only been doing mystery shopping for about five months, and have being enjoying it. There are a lot of legitimate shops out there, and I've signed up for a couple dozen. I found most of them on the Mystery Magazine's list of 100 top MSC's. I don't get offered assignments for all of them, and I don't accept all the ones that do get offered.
That's the beauty of mystery shopping - you can pick and choose if and when you want to shop. I tend to stay within my city limits, and can usually schedule a couple for the same day in the same area, to save gas and travel time. I also don't over-schedule, as you have to remember that you have to do your reports at the end of the day. Even the types of shops that you do regularly still take time to write up. But you'll get better with practice.
I also save my write-ups in a document, because some of them are so similar, you only need to change a few of the details each time. Especially restaurants that you return to several times, where you have to describe the texture of the hamburger patty, the bun, and the fries, or how clean the washroom was.
So go ahead and sign up for a few, just to test the waters, and then decide if it's for you or not. There wouldn't be so many of us still out there if it was so bad. Don't let that scam take away what could just turn out to be a very good thing!