Answer:
He is obsessed with the ring, like many others before him, he did not like the party or the people that much and thought about his ring which is why he often used it when he wanted to leave.
Considering that everyone knew Bilbo and was accustomed to his wild stories of adventuring, they tend to believed that it was just another one of Bilbo's tricks, even though it was a bit awkward for them that he disappeared in such a manner.
Explanation:
Bilbo had the ring for years in which he used it only when he needed it since he can never separated himself from it.
He is obsessed with the ring, like many others before him, he did not like the party or the people that much and thought about his ring which is why he often used it when he wanted to leave.
Considering that everyone knew Bilbo and was accustomed to his wild stories of adventuring, they tend to believed that it was just another one of Bilbo's tricks, even though it was a bit awkward for them that he disappeared in such a manner.