The last time your property was surveyed was probably when you bought it. If you merely paid for a mortgage survey, the mortgage company would have used it at the time but not retained it. It is merely an opinion that the value of the property is worth at least the value of the mortage. If you had a Homebuyers survey you would have to identify the name of the Surveying company and approach them; they probably will keep it for 6 years.
But I don't see how having the last survey helps at all with putting a pool in.