As Mason was slow dancing with different partners, he got surprised when he felt a bigger figure in his arms, a figure that'a bigger and taller than an average woman.
And if there was a woman that's actually this strong and tall in the hall, he would have noticed her presence when he came in.
This is why it means that whoever he is dancing with is a man.
At first, he was ready to laugh it out with that man, but he instantly changed from finding it as a funny accident into shock when he heard the man whispering " Did you miss me, baby?"
Mason immediately recognized that voice, it belongs to Matthew.
The reason why he didn't recognize him quickly, because first of all he was not focusing on his partners' faces that much and second of all Matthew looks drastically different from the last time he saw him.
