The choice for an ad hoc query, a parameterized query, stored procedure, or sp_executesql are not made internally by SQL Server. They're all made by the application. There's nothing in SQL Server that would take a prepared statement and turn it into sp_executesql on the fly. I'm not an expert with Solarwinds Ignite, but I wonder if there is a setting or aggregation or something that is taking the invidual statements being executed through sp_executesql and turning them all into a single aggregate under the sp_executesql heading? That's where I'd look.

Oh, and update the instance of SQL Server. There are tons and tons of bug fixes in the SP and CUs. Running RTM of 2008R2 is almost criminally negligent at this point in time.