How far should a teacher investigate?

[PD-Jnr]

Alright, Last night there was a fake twitter account made of me tweeting about inappropriate things. One other students name was mentioned. I'm not really bothered as it is a few friends having as laugh. However today in last lesson someone shouted "Sir, Do you use twitter and have you seen the @TwitterNameHere?" He replied saying "No" and took out his phone during the lesson to find out what is was about. The lesson came to a hault and he began to browse through the 14 tweets while everyone was talking and not filling in a sheet. He was laughing at some of the tweets and then asked if a student who had tweeted about the account in lesson time was in the classroom next door.

He left our classroom unattended and asked the student if it was him. Which it indeed wasnt, he then asked another pupil who had tweeted about it off them. He then got them to show there twitter which were both logged into there personal one. He then took one of the pupils phones and walked back into the class putting it on his desk. He has said that he will need to contact the Senior Staff. (He is only a music teacher)

Do you think he should be consulting the Senior Staff?
Should he be checking what students are tweeting on twitter?
Does he have the right to view a pupils phone?

Tomorrow we have been told that we will most likely have to write statements but I do not want the matter to go further, it was a joke afew friends had about me, nothing too serious. How the school has began to talk about it and its spreading fast. Around 6 people have removed everything about the twitter account from twitter etc and added privacy blocks to our accounts.
The teacher is the one who wishes for this to be taken further without consulting me in private. I really dont wish for it to go further. We are over the age of 13 so we are legally allowed twitter/facebook aswell etc