floridagal, The inventory in Journeyman Project Turbo can be cycled using the up and down arrows on the right hand side of the inventory area. Perhaps you grabbed some other things to cause it to be below the three (think that's how many are listed at a time as been ages since played this game) in the inventory at present time?
NOTE: I noticed you said key, so assume you don't mean a bio chip? I should point out that bio chips don't get used in the regular inventory area but in the bio chip area which is toward the bottom of the screen and can be viewed (expanded) by clicking on an arrow next to the navagation controls. Here's a great image that labels everything for the game at Games Domain