I thought in Texas all private land was posted even without a sign.
Kinda yes, kinda no.
§ 30.05. CRIMINAL TRESPASS. (a) A person commits an offense if he enters or remains on or in property, including an aircraft or other vehicle, of another without effective consent or he enters or remains in a building of another without effective consent and he:
(1) had notice that the entry was forbidden; or
(2) received notice to depart but failed to do so.
(b) For purposes of this section:
(1) "Entry" means the intrusion of the entire body.
(2) "Notice" means:
(A) oral or written communication by the owner or someone with apparent authority to act for the owner;
(B) fencing or other enclosure obviously designed to exclude intruders or to contain livestock;
(C) a sign or signs posted on the property or at the entrance to the building, reasonably likely to come to the attention of intruders, indicating that entry is forbidden;
(D) the placement of identifying purple paint marks on trees or posts on the property, provided that the marks are:
(i) vertical lines of not less than eight inches in length and not less than one inch in width;
(ii) placed so that the bottom of the mark is not less than three feet from the ground or more than five feet from the ground; and
(iii) placed at locations that are readily visible to any person approaching the property and no more than:
(a) 100 feet apart on forest land; or
(b) 1,000 feet apart on land other than forest land; or
(E) the visible presence on the property of a crop grown for human consumption that is under cultivation, in the process of being harvested, or marketable if harvested at the time of entry.
(3) "Shelter center" has the meaning assigned by Section 51.002, Human Resources Code.
(4) "Forest land" means land on which the trees are potentially valuable for timber products.
(5) "Agricultural land" has the meaning assigned by Section 75.001, Civil Practice and Remedies Code.
I emphasized two scenarios which have no mention of signage or fence requirements. I would dang sure let the county Sheriff's office know who the owner of the property is.
BTW, the three vertical lines thing was news to me. I do not recall ever seeing that and I have a LOT of bush time here in Tejas.