A birthday celebration of my professor

Sunday afternoon I received a text message from my professor (who is the vice president for administration and finance in a certain university) inviting me to attend his 44th birthday celebration today - Wednesday. At that moment, I felt blessed and happy. I thought everyone was invited but when I arrived at the venue, only four of his students were invited. The rest of the visitors are his colleagues from different universities and government officials.
I gave him a simple gift and I just hope he will like it.