Not So Sure (Fooled by eyesight?)

This happened when I was in high school, this story was true to live story...I guess...well...
I'm not scared anyway...I don't believe in ghost either...
but then everytime I remember this story there's some questions popping un in my mind...
was it a ghost? Or an illusion maybe?

Here how it goes...

It was morning then, a bright shinny day for me...
my father ask me to took care of our shop, it was actually a hardware store - it's
where you can buy stuff like paint, hammer, nail, sandpaper etc...that turns into a shop
that repairs electrical appliances...
Then since it's early morning, the lights are off...
I was watching television...
Then there were two wooden office table in our shop that contains two huge televisions above it,
about 19 to 20 inches of size each...
It was located on my right side, about 4 feet in distance...
Between the T.V.'s there was a gap, I think about an inch or two...
since I've been watching T.V. near at the table...
in my peripheral view I saw a woman between the gaps, behind the tables...
wearing violet blouse and used to fixed her hair...
I thought it was my mom, because every time my mom was about to leave the house
she used to seat on the chair behind that tables with T.V.'s to fix her hair...
then I stood up to get some water...
the path was beside the table...
I walked straight beside the table...
In my mind, and since I saw it again and even saw the woman as a whole in my peripheral view...
I really thought it was my mom...
I even ask her where she will go while I'm passing through but she doesn't speak up...
so I walk through and went inside the house to reach the kitchen...

and guess what...

my mom was there... and took bath of our dog...
she's even wearing red duster which she used to wear when she's at home...

How come that I've saw her before wearing violet blouse?...

then I ask my mom...

'mom what are you doing here?..
how come that you're here wearing another clothes in just a sec?...'

my mom said...

'what?...Are you crazy?..I've been here since early...'

I just pause for a while and think...
I'm not that sure, my probability is just 80 to 90 percent since I only saw it on my peripheral view...
since then, though I don't believe in ghost there were some instances that I doubt...
Does ghost really exist?
Then I just told to my self that they are just part of illusions....