Indigo Airlines - Unfair additional charges

I had booked Mumbai to Delhi flight on **/**/** no. *e**** Pnr eg*vxm. I had done web check-in. I entered the cost t* Mumbai airport, showed a boarding pass, cleared security check, got it stamped. I moved to gate ** showed a boarding pass which was barcode scanned and cleared. I entered the bus. Meanwhile, I somehow lost my boarding pass accidentally while boarding the bus. While entering the aeroplane I realised that the boarding pass was lost. I informed this incidence to the personnel checking gate pass and letting passengers inside the plane. I showed him the boarding pass web check-in copy with all the details. But he refused to allow entry in the plane. I was sure the boarding pass was lost just where the bus started but he wouldn't allow me to go and check neither did he send anybody to check for the same. I tried to convince him saying how could have I reached the aeroplane gate without having my boarding pass and without security check! I even told them how important it was for me to board the plane me being a doctor sent on an urgent deputation. But he and another guy just turned a deaf ear even after talking to somebody on wireless they didn't allow me to board the plane. Rather I was sent back in another jeep back to the entrance of the airport.
There I informed the receptionist about the incidence. She said she will accommodate me in the next flight *e but charged me a whopping amount of Rs ****. I again had to go through all the previous steps starting from scratch to board the next plane.
My complaint is they should have allowed me on the first plane itself and if that didn't fit their bill at least they shouldn't have charged me an extra amount. This is looting the customers! A leading company like indigo is not expected to cheat their passengers in this way. Such incidence could happen with anyone. Least I could ask for is my additional amount paid to be refunded back.