Yes, swans recognize people, especially the ones with the daily or frequent food bucket! You probably did not cause the cygnet's death as if the demise was due to a predator, a predator will find them no matter the location.

The next time you feed the swans, show the birds the food bag and walk them back to the area that you know they inhabit. Swans will follow the food. You can also go directly to their habitat area and let the swans know that this will be their feeding site each time you appear. The Regal Swan