It may have just been lucky.It may have been a mouse,coon or possum that uncovered the trap.
Remake the set.Are you using a sifter to place dirt over your trap?
You may also consider setting snares in the coyotes travel ways.
Yes I am a trap supply dealer.
Yes I have Lenons Muskrat,coyote,fox,Bobcat,fisher and Marten--4 ounce lures.
Also Blackies Blend ,his entire line of 1 and 4
0z. lures and his baits .Also my MoundMaster beaver Lures.
Wiebe knives and fleshing tools ,Too.