It is OK to dig around a bit, and see if something turns up - I do, but I don't get too concerned if I can't find something obvious.
Sometimes you will find it is an off market transfer, which is being announced to the market on a certain day - often not the actual day the agreement between the two parties was reached, and so it is at a slightly different price to where the stock is currently trading, which causes a price and volume spike like that.
This type of issue is not really a concern and will not affect the current trading, it does however it does make the analysis more difficult, especially when you are analysing a stock for the first time. It also reinforces that you need to be fairly closely in touch with the instrument (stock) you are trading, so as to better understand the price movements.
