that one "snuck up" on me

This past weekend we went down to Morrisburg on the St Lawrence River to witness a re-enactment of a battle in the War of 1812 - a decisive battle that repelled the American attempt to annex Upper and Lower Canada into their new United States. Beside Upper Canada Village, at Crysler's Farm, a large number of "actors" (actually military history enthusiasts) dressed in period costume had set up a military encampment. After the re-enactment of the battle we wandered among the tents, learning about the hard life of some of the soldiers, checking out the various merchantile establishments, and observing the settlers at work making candles, cooking meals, and cleaning muskets. Mitchell and his friend each bought a wooden musket that they could sling over their shoulders. I asked Mitchell what other wooden guns he had seen for purchase and he said "We saw one like the one I have at home but Daddy says we have to sneak on that one." I asked him to repeat what he said a number of times trying to figure out what he meant. Finally I asked Mike what he had told Mitchell; what he had said was "We will have to "pass on" that one this time, buddy." Hard expressions to sort out: "sneak up on", "sneak past", or "pass on."