In-band network telemetry (INT) is a new network measurement technology that uses business packet to collect network information hop by hop. Since business packets may be lost due to various reasons, INT telemetry information will inevitably be lost. Unfortunately, telemetry system is not aware of this loss. In this letter, we present FindINT, an INT packet coding scheme with two marking strategies, to measure per-flow packet loss rate and location. FindINT is inspired by alternative marking method, which is triggered by loss event instead of polling.Experimental results show that FindINT has extremely low overhead and high detection accuracy.