Yes extralateral (one word) rights are still in effect. A lode claim has the rights to the dip of the deposit that extends laterally outside the the surface lines of the claim along it's long (strike line) sides.
There is no requirement that the vein be exposed on the surface. Once you establish that there is a valuable mineral in place (the discovery point) you will need to determine the strike line (compass direction) of the deposit so you can orient the claim up to 300 feet on either side of the strike and up to 1,500 feet along the strike. You can drill (or dig in some circumstances) as needed to expose enough of the vein to establish the strike line (and dip) of the deposit.
If you have only determined the point of discovery and not the strike of the vein before you locate you run the risk of laying the claim out in the wrong compass direction. Doing that has sunk many a locator. If that is the case your extralateral rights are lost because the short ends of the claim do not have extralateral rights. Only the long sidelines parallel to the strike have extralateral rights.
It's tricky business locating a lode claim properly.
As with most claims the odds of striking it rich are not great. Most veins tend to "pinch out" at depth leaving the locator with little but a hole in the ground. On the other hand the richest gold discoveries in history have all been lodes.
More about
Strike and Dip.
Heavy Pans