Not necessarily. A hiker who inadvertently ends up on private property without encountering trespass warning signs or boundary fences cannot be legally accused of trespassing. The reason being, tort/common law, assumes the absence of trespass signs or a boundary defining fence is synonymous to acceptable entry onto the property. However, this tort law applies to daylight hours.
On the other hand, if the hiker had encountered a fence or sign prohibiting entry, he/she may be legally charged for trespassing onto private property. The argument that he/she was lost before winding up on private land would be effectively nullified in this scenario.