Narrative:

At approximately XA30 on oct/mon/02, I proceeded to service the engines on aircraft X. I started with engine #1. I svced and inspected #1 engine. I proceeded to #2 engine and did the same as #1. #3 engine was the last one I inspected and svced. To the best of my knowledge, I had put the cap back on and closed the door. I guess this wasn't the case. When the aircraft arrived in ZZZ1, the door was gone and the cap and chain were hanging outside of the door opening. The cause of this incident was just a case of not rechking oneself. I have always made it a point to put the caps back on. This is my first incident in this situation. There was no WX or any other distraction.

Google
 

Original NASA ASRS Text

Title: A B727-200 WAS DISPATCHED IN NON COMPLIANCE WITH #3 ENG OIL SVC DOOR MISSING AND OIL FILLER CAP NOT SECURED.

Narrative: AT APPROX XA30 ON OCT/MON/02, I PROCEEDED TO SVC THE ENGS ON ACFT X. I STARTED WITH ENG #1. I SVCED AND INSPECTED #1 ENG. I PROCEEDED TO #2 ENG AND DID THE SAME AS #1. #3 ENG WAS THE LAST ONE I INSPECTED AND SVCED. TO THE BEST OF MY KNOWLEDGE, I HAD PUT THE CAP BACK ON AND CLOSED THE DOOR. I GUESS THIS WASN'T THE CASE. WHEN THE ACFT ARRIVED IN ZZZ1, THE DOOR WAS GONE AND THE CAP AND CHAIN WERE HANGING OUTSIDE OF THE DOOR OPENING. THE CAUSE OF THIS INCIDENT WAS JUST A CASE OF NOT RECHKING ONESELF. I HAVE ALWAYS MADE IT A POINT TO PUT THE CAPS BACK ON. THIS IS MY FIRST INCIDENT IN THIS SIT. THERE WAS NO WX OR ANY OTHER DISTR.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.