Back when I lived in Libertyville and had a garden, I, too discovered a toad on the premises. I wanted to keep him or her there, and went so far as to look up a herpetologist and ask his advice. He told me to purchase a pottery toad house -- basically a terra cotta cone or beehive with a hole cut through it to make a door -- and to place that there at the edge of the garden to give the toad a place to relax and cool off. I did it, and the toad loved it. Stayed there a whole year, then set off, never to be seen again.
JiLS