wow, wierd night, it must be because i had a strange one also.
I was a sleep and my missus rang me to pick her up from the shop, dogs were a sleep beside the bed and i was dazed from being woken by phone, i went for a piss as you do when you wake up, heard what sounded like my back screen door while i was taking a leak, but the dogs didnt hear it as they didnt wake up, but i was then on alert.
 
stuck my head out for a quick look after my piss, but didnt see anything, the dogs are usually good at protecting the yard so thought it was just me being half asleep.
got in the car picked up the missus which took the entire 3minutes, when i left the house to get the missus i took the dogs with me. wish i left them behind.
but when i got home the missus asked why the side gate was open? this gate is never open its a big gate that is wired up, i freaked out and quickly went for a proper look around the yard expecting to see some one and prepped to sneak up and clobber them.
So some one was in my yard and did try and enter my house when i was taking a piss,
this is the second time in a week i have had the suspicion some one was trying to enter my yeard,
the other night at 2am i thought i heard the side gate and talking and the dogs went out for a bark and a grawl. when i looked i couldnt see any one. thought the dogs might have scared off some kids that were just on the street but after tonight i know some one was in my yard,
I suspect what has happened the person was entering my house as the missus rang and heard me get up for my piss and quickly snuck out the door they were entering and hid in the dark of my yard untill i drove off and they left out the side gate, as i locked the back door after i checked and before i left the house.
I was bloody dead certain i heard my screen door, and i was thinking if this guy trys to sneak up on me right now he will cop some serious piss,
 i was pushing that piss out fast so i could go check the door. lol, and lucky for them the dogs didnt hear them.
i gotta say i was a little freaked out when i saw the gate open and know that some one was actually entering my back door,  

your story is very similar to mine, its a horid feeling when you feel some one is around in your personal space. the adrenaline goes crazy, when i heard the screen door open i was pissing pure adrenalin i recon, and when i got home and decided to enter the back yard i got a second hit of adrenalin i kicked the gate so if any one was behind it they would get collected by it, and all you can do to over come the adrenalin is make sure you talk your self into committing your self into a fight.
I have never had any one try and get into my house before especially while i was home asleep it makes you bloody angry or scared and you have to pick which one you are going to be.
its a very curious feeling now that i think about it, you almost get a choice with your brains emotions weather you should be scared or very angry.   i should say im having trouble sleeping now.