Welcome!
Are you sure it was a smart app and not a device type handler? They get installed into different places in your account library.
See the following custom code FAQ and check the steps to make sure that you were doing the one that matches the code that you are trying to use.
( and don’t worry if you weren’t, we’ve all made that mistake at some point. 
)
If you do have the right process, then ask your question in the thread where you found the code, since that will be the fastest way to get an answer.