Do NOT throw it in the "bin." First try converting it into an internal drive. An internal-to-external adapter for troubleshooting is highly recommended. Yesterday I dropped a WD Elements drive and the power light blinked but it was no longer recognized. I opened the case and disconnected the SATA-to-USB adapter, seated it into an Eagle Consus case and reconnected it to nominal SATA cables, and it worked fine. Upon closer inspection, the mini-USB port on the stock adapter had been torqued out of its solder in the fall and prevented it from spinning up.
If after you remove the internal drive it is still unresponsive, then yeah, it's probably physical damage to the disk. But unopened, the actual hard drive itself is often hardier than you might expect.