Use text to stay in touch with connections?

I had a great networking phone call with a BB associate this summer and part of our discussion was about an interview I had for the fall semester internship. I recently got the internship and would like to tell him the good news.

But I was wondering if text is the most appropriate way of telling him? I originally reached out to him on Linkedin and he gave me his phone number on Linkedin. He actually postponed our phone call over the summer by one week because he was busy but he was telling me through text and we rescheduled using text. So I'm wondering if text or linkedin is more appropriate (I never emailed him btw)?

Sorry if this is a stupid question. I just started my sophomore year and I started networking over the summer and I know it's important to keep in touch with people so this will be the first time I will be sending those "stay in touch" messages. Thank you for any help.