I think it happens to everyone in some situation (It doesn’t even have to be in matters of love. It can be that guy at the office that says he has no idea why the color printer is out of color, when you know very well if you checked out his desk it would be as fantastically vibrant as a tropical National Geographic Magazine issue…happened). 
You might not have the proof, but you just know when something is amiss.
So what do you do? Do you:
a. Be straightforward and risk that always novel concept of adulthood and honesty? (Did your Blood Pressure rise when you read that? Mine did when I typed it.)
b. Skirt around the issue ?(you kind of bring it up, but not really. Its more like a babble, a bubbling brook if you will, where you ask nothing and gain nothing. Picture someone singing tralalalalalala on repeat as you say wishy washy things like “you know that girl that always texts you at 1, 2, and 3 am and asks what you are up to? Yea the same one that returned your belt after Saturday night. I well I just you know because well I mean right? “Good talk” Ugh!) 
It’s especially good when dolls surround it.
c. Ignore it and continue on (Of course it could be the first time in a gazillion that your gut isn’t serving you correctly. Maybe it was that weird Slavic food you ate for lunch? They have food poisoning and parasites in Croatia and Bratislava. It’s just indigestion, He didn’t really just leave with that random blond girl. He was outside waiting for someone else. Although potentially dangerous Slavic is totally the new Thai.).
Pop out of that crotch and go girl go!
d. Ignore it and Run Baby Run (cue Dixie Chicks “Ready to Run”. That guy didn’t deserve to be graced with a conversation. He isn’t worth your time. Clearly they might have disrespected you. Maybe?? Your stomach and most of your small intestine were all in on that decision and what are the chances they could be wrong?? In my opinion not very good, but to be fair it might be nice to have some facts behind all of these assumptions (Both from the person in question and the people in the know. Not quite ready to talk to your belt-less friend? Enter my ever-growing romance with Google (Bing who?). It is actually pretty interesting stuff).
So on an initial look-see on lies and their detection, most articles start with “Lies are extremely difficult to detect.” Awesome and informative. Wow! Pressing on, what we do know is that most people are supposedly no better at lie detection than chance (so 50/50). However while in a testing situation that is probably true, when it is someone that matters to you that seems like it might not hold up. Keep reading and BOOM! Validation! “Rely on intuition. People may be better at detecting lies with their intuition. Implicit or broadly unconscious processes can be more effective than conscious directed thought.” (YEESSSSSSSSSSS!!!!).
If that wasn’t enough to set you free you can always rely on Oprah (I vomited in my mouth a little just now and started craving bonbons and a job that allows me to watch Dr. Oz) and go chunking (no no don’t vomit, although if you are the nervous type and your belly is already uneasy because of absurd relationship shenanigans that could definitely be a valid response).
Chunking(from Dr. Herbert Simon): As knowledge accumulates (about a person) you begin to recognize patterns. Your brain unconsciously organizes these patterns into blocks of information. This continues overtime and eventually stores in your long-term memory. So a tiny detail sets off a spark to the larger picture and ALAS!! Intuition! You know you are right. Now what to do?
When your person texts you later that day/night with something happy, light-hearted, etc, you could respond “She’s ugly” or something equally amazing emoji style:
Them: Super excited to see you tomorrow!
You: (Turban guy emoji followed by that new weird not quite smiley faced fanged cat emoji) 
Nothing says displeasure quite like an ethnically dressed man followed by a cat.
In reality you should probably be honest and not aggressive or sarcastic (Hello fancy social media world still looking for a 
font that equals sarcasm) and follow my best friends advice:
whatreallyhappenswhennotlooking 