You present an interesting problem. First you seem to have mixed several terms regarding your septic system which refer to different types of systems. 

When the previous owner replaced the septic tank, did he replace the drainfield also? It would have been likely to have done both at the same time. 

You wrote about a "holding tank". A holding tank is generally used only where the drainfield is higher than the septic tank and the water has to be pumped, or perhaps siphoned, to a higher level. Is your drainfield at a higher level? Is it possible that when you wrote of a holding tank you were talking about the spetic tank. If this is so, I do not understand why they wre not able to find it. Generally a metal probe is used to probe until the tank is found. It is generally in line with the exit line from your house.

Drainfields generally consist of two types. There is a drainfield with lateral lines to distribute the water and there may be a drywell in some older homes. This is generally a pit of some type which collects the water and allows it to drain through the bottom and sides. Pits may be just holes in the ground or may be more structured with a concrete dome like a "honeycomb". The lateral system has drain lines which are laid on top of stone and then covered with earth. The lateral lines are generally 18-30 inches deep. They are connected to the septic tank by a distribution box or use a header line in the middle of the field. There may be other configurations depending on what the standards are in your area of the country.

Unless you have a pit of somekind, there is unlikely to be a "lid" to inspect the field. Some pits may have lids, but many do not.

In order to better help you, I suggest that you give me a call at my toll free number (888) 352-7226.