I cannot find audio file downloaded via hike, so please suggest where it is saved. I am using nokia lumia 620.
Go to the Microsoft store and download the Files app. This is a file manager application. Use that to browse through the files on both your phone, and your Micro SD card.
After that, use the search feature of the app to look for a folder written "Hike", or the name of the audio file, if you know it. Long press on the audio file, then click "browse to item", to navigate to the folder that Hike saves all the audio you acquire through the app.