For the most part, your young green iguana will seem perfectly content basking in the glow of the heat lamp in its enclosure as long as you keep serving up the fresh food and cold water it loves. But just because your juvenile iguana seems content, it does not mean it will not make a daring escape to explore the rest of the house if given the opportunity. It is not at all uncommon for a person to come home to find their iguana missing in action, seemingly nowhere to be found. If this happens to you, gear up with a flashlight and some fresh greens—chasing down your valiant lizard is probably not going to be simple. There are a few things you should keep in mind while you search. 

The house must be put on lockdown. 

Close up the windows and bar all the doors. With a juvenile iguana on the run, you just can't take any chances on it making an escape to the world outside. If your iguana happens to slip out through a window or crack in the door, it will most likely hightail it to a tree because green iguanas are arboreal (or tree dwellers). Unless you have a bucket truck on hand and some uber cool tree-traversing skills, a young and agile iguana in a tree is not a good thing. 

Looking for an iguana on the run takes patience and thorough attention to detail. 

Iguanas have this awesome ability to kind of just naturally blend in with their surroundings. It is not so much that they shift in color hue dramatically (green iguanas only shift color slightly), but they can sit absolutely still and maneuver their little bodies to conform to all kinds of shapes. This means that you could search the house over and never spot your iguana. The best way to look for a loose iguana is to search room by room and this must be the most thorough search you have ever conducted. Flip over mattresses, take apart furniture, move everything that is sitting still to take a look. Once you are positive one room has been looked over, seal it off by closing the door and stuffing a towel under the crack at the bottom.

If you create a heat source, your iguana just might come. 

Iguanas love the heat of the sun or just their heat lamp, which in their world is pretty close to the same thing. Create an atmosphere of darkness in the house by drawing all your blinds and covering the windows. Situate the heat lamp in the middle of the house and turn off the lights. Your little lizard may come out of hiding because it is attracted to the heat of the synthetic sun.  

If you have finally found your iguana after several days, you may wish to take it to a veterinarian to make sure it's in good health.