There were only three available at the fair. You would normally only buy bowls in a set of four. However, as you mention, you really like this particular style. Perhaps you liked it so much that you made an exception in this case and bought the three because that was the maximum available. But then you lost the third, and so the memories you were triangulating from were "there are two in the cupboard," "that's not the full set," and "four is a full set."
Now onto your spouse's memory. They remembered two at first, because they were triangulating between "we normally buy four," "there are fewer than four of these," and "we always buy an even number." Confronted with the existence of a third, the other memory, "there are fewer than four" remains in effect.
And do you know what she says? “We’ve only ever had three.”
It’s been many months now, maybe a year, and there’s still only three, but hand to god, I’m going to find that fourth bowl.
I still can’t get a straight answer out of her why she’s so certain there were only ever three when she was just as certain there were only ever two until confronted with the physical reality of three bowls.
Now she thinks this is about being right, but I insist it isn’t. It’s the unsettling idea that my memory isn’t correct.
I may just have to let this one go... :-)