Or was it accidental?
To make sure, Johnny got out the circular which Tomaso had seen, laid it where he remembered it to have been that day, and sat down at the table where Tomaso had been sitting.

He placed the lamp where the light fell full upon the paper and studied the letterhead for several minutes, scowling.
Tomaso, he decided, had remarkably sharp eyes.

Seen from that angle, the letterhead was not conspicuous.

The volplaning machine was not at all striking to the eye.

Unless a person knew beforehand what it represented, or was looking for something of the sort, Johnny was forced to admit that he would be likely to pass it over without a second glance.
Tomaso, then, must have come there with the intention of leading adroitly to the subject of airplanes.