Two or three years ago, I had one of my most aggravating summers over the griefiest, stupidest thing ever. I came home from work on a very hot summer day, and the minute I opened the door, I was slapped by the most horrendous stench. So I covered my nose thinking "omg, what the heck?!" as I headed straight for the kitchen. That had a very distinctive smell of rotting meat and I figured I had probably forgotten something on the kitchen counter and the extreme heat did a number on it.
Trouble is, get in the kitchen, nothing suspicious in sight. At that point, I'm almost gagging, so I open all the windows and all the doors to let some fresh air inside. Then I methodically search every nook and cranny in the kitchen. I open every cupboard, the fridge, the oven, move both of the latter to make sure nothing fell behind them. Nothing...
The smell clearly seems the strongest around the fridge but despite my best effort, I find nothing. I look through every other room to no avail then back to the kitchen for a 2nd thorough search but nada. At that point I figure maybe it's something from the pipes, but it's too late to call a plumber. He drops by the next day, takes a whiff and goes "nope, that doesn't come from the pipes". There is something decomposing somewhere. But knowing I've checked everywhere, and since I'm gonna pay him anyways, I ask him to have a look through the drains and everything just in case. He does and as he predicted, nothing.
A couple more days of this, including a cancelled dinner because I am just too embarassed to have friends over under these conditions, I suddenly think of checking the dryer's air vent. I remember my mom used to have issues with birds nesting in hers and thought maybe one died in mine or something similar. But nope. This nightmare went on for a few weeks then the smell just faded away on its own, and one day it was gone. While I was happy, I was also really upset and concerned that I never found it because it could very likely resurface at some point in time.
About a month later, the light bulb near the sink area in the kitchen went out. Having a cathedral ceiling, I had to get a small ladder to reach it. So after I removed the ceiling light fixture, I turned to put it on top of the fridge and noticed a small white tray with something dark on it sitting at the far edge of the fridge. I remember saying something in French that could be translated as "are you freaking kidding me?!" but in a very unlady-like fashion.
There it was, a steak I took out one day, while trying to reach something else in the freezer and that somehow got pushed all the way to the back. And I was so angry with myself because I had checked the top of the fridge but didn't climb on anything to see all of it. It was a very big and tall fridge. I just had a quick glance from where I was standing and blindly patted the top as far as my hand could reach which wasn't all that far, despite my 5'8". I mean, to have been this thorough with everything else and so careless with this one... Granted, I NEVER put anything on top of the fridge except for the occasional quick swap of items so I had no reason to expect this and yet...
So you're wondering why the heck am I telling you this? Because to me, bug fixing is a little like that infuriating incident. You are faced with an unpleasant situation and follow your nose to the source. Sometimes, you're lucky: the problem is sitting right there on the counter and you can just dispose of it however is most fitting. Sometimes, it just fell between the stove and counter. Move the stove out of the way, and bye bye problem.
But sometimes, it will be sitting on the far edge of the fridge, at that one place you will never think to look. You know the problem involves the fridge and you'll look inside the fridge, around it, under it, behind it, you'll even empty it and trash everything inside, but you'll never think to look at the back edge. And because sometimes, just like in my incident, its properly wrapped and therefore doesn't leak or trigger any other visible sign that could point you to the back edge. So you'll resort to the most far-fetched and improbable alternative causes, like the pipes and air vent. And it will take a burnt light bulb, sometimes weeks, months or years later for you to finally see where that darn thing was sitting all along.