Yes, this could be the reason. A man's actions generally dictate what you can expect from him in the future. You can always be subtly flirtatious, making quiet, slightly prolonged eye contact with him. This way you aren't saying anything that he would verbally outright reject you for. If he is interested after eye contact you will know. In the meantime, I would remain friendly and communicative as you are already doing. I would not initiate a lengthier conversation if you feel he is going to keep it short.