A Mechanic reports a CRJ-700 he worked on the night before; had returned to field with a Slats Fail Caution message. A Skin Spoon tool was found wedged between a slat and the wing lower surface. Mechanic had placed the Skin Spoon on the lower lip of one of the slats; but the tool did not have a Red streamer attached.

Narrative

I showed up for [shift] turnover and was assigned to Aircraft'X'; a CRJ-700. I was then made aware by my Lead that Aircraft 'Y' was at the gate and was having starting/APU/bleed air problems and was needed for revenue. So; I rushed to the gate with my tools and got busy troubleshooting/fixing the issue. Because of the associated Cowl Anti-ice Cautions; the Pilots didn't feel comfortable taking the aircraft and were reassigned to Aircraft 'Z'. After talking to my Lead; we decided bringing Aircraft 'Y' back to the Hanger was our best plan and that way; since I had troubleshot the problem to an APU Load Control Valve; my Lead would have another Mechanic change it out. While driving Aircraft 'Y' to the Hanger; I noticed that the Center tank had 1300 lbs fuel; often an indication of a leaking Ejector or other internal fuel lines. After parking Aircraft 'Y' I headed back to the gate to get Aircraft 'X'; drove that aircraft back to the Hanger and parked it inside for troubleshooting and other maintenance.I then went back to Aircraft 'Y' and defueled the Center tank. I had the assigned Mechanic sump the Center tank and made him aware of the leak check procedure. I then went back to Aircraft 'X' and started troubleshooting the right-hand Wing Slat Status Message MEL. While doing the checks on the slat skew sensors with a multimeter and a cheater (my skin spoon); several people had been coming up to me with questions: Mr. 'X' needed screws or a Part Number for them; Mr. 'Y' needed help with issues for a Detail Visual Inspection (DVI) of the Rudder Travel Limiter; Mr. 'Z' needed help with how to do the lubrication of the APU door actuator; Mr. 'W' couldn't get our aircraft to take oxygen. I let myself get distracted from my own work/focus and set the Skin Spoon on the bottom lip of the slat right by were I was working. When it got close to go time (the XA.00 hanger shuffle); Mr.'V' started hollering about how long it was taking. I was trying not to be the bottleneck; so I quickly re-paneled my aircraft; sucked up the slats; checking for Maintenance Diagnostic Computer (MDC) messages; pulled electrical power; moved my tool box; ran out; grabbed a Tug; and relocated the CRJ-700 outside. I then came back in and completed my paperwork; continuing the MEL since we didn't have parts. I then took a short break and put my toolbox back; not realizing I was short a Skin Spoon. All the other tools I had used I [believed] were home safe and sound. A fellow Mechanic was assigned to troubleshoot a Slats Fail Caution message and had made me aware he had found a Skin Spoon lodged in the slats. Since I had been there the night before I checked my tools and was unable to locate one of my two Skin Spoons. I feel the event happened primarily because I let outside factors/distractions; dictate my normal system of checks and balances. Another way to say it would be that I let the situation control me instead of controlling the situation. I came forward to the Supervision and let them know that I believed it was my tool that caused the event. The problem with the aircraft was rectified. My suggestions would be: 1) Do not let situations take you out of your game. 2) Never use an aircraft as a workbench.3) Obtain a company issued tool from our stores with a streamer on it 4) If using my own tool; affix it with a streamer.