Sometimes your counterpart tells you he sent a SWIFT payment, but the funds are not credited to your account yet. Here is the guide on how to validate a SWIFT payment and make sure funds have been really sent.
First of all, until you have received your SWIFT payment (you can't see it in the list of transactions in your internet/mobile bank) you can't be sure in this payment. Even if your counterpart provided you with correct MT103 confirmation form, still there is a chance he simply asked his bank to recall the payment.
However, you can try to track and validate payment in order to make sure it was really sent. Go to TrackMySwift and put all the details from your MT103 confirmation form. Normally, one tracking attempt costs $2.49, however you can use a monthly subscription if you send/receive cross-border payments on a regular basis.
While TrackMySwift allows to track by both UETR and a reference #, try to check it separately. If a payment is tracked by both UETR and a reference # - more chances it is real.
Also, when tracking by reference #, normally amount is validated as well. So you not only will be able to check if the payment was sent, but if the value of the payment is real.
Third, check the number of trackings:
If there are a lot of people checked this payment by UETR or reference # you have more reasons to question an integrity of your counterpart (yes, there is a lot of scam in cross-border payments).
What If The Payment Is Not Trackable?
Most of the payments in USD/EUR are trackable at TrackMySwift, however there are rare exceptions. You can check if UETR code is valid. There are certain validation rules for UETR code and if you see that there is a mistake, probably it is a cheap scam.
Anyway, you will know the answer when the payment will be credited to your account. Don't trust photos and videos of payments which you can't even track.