I manage the relationship with one of our key vendors e.g. an enterprise resource planning software such as SAP. As such, I initiate and look after negotiations, issues, new products, opportunities and everything surrounding our work with "SAP".
Our new senior managers (CTO, COO, etc. level) have started meeting these people without me to discuss strategy as well as just socialize - reportedly also because they have some common contacts in college -, but never keep me in the loop - they just fleetingly mention a joke or two about them and some decision they made together.
What happens thereafter is that whenever I communicate with "SAP", they know something about us that I didn't know, or a new product or strategy we are going to implement... about which I didn't know. The communication is quite embarrassing.
While I find it slightly degrading in itself that they initiate communications without even informing me, I think it would be beneficial for all parties to at least keep me in the loop on whatever decisions were made, what information was shared and what new information we know.
Ultimately, since I am responsible for the relationship with "SAP", how can I ensure that I am always in the loop in such circumstances?
Clarification: note that I was hired specifically to manage this relationship and and the ERP/software delivery (it is an exclusive relationship - we use only one type of software platform) - there are other vendor relationships but in completely different business functions; I couldn't change to them and there are people managing those relationships already. In essence, I am an "SAP"/ERP "expert" or "super user" as well.