Running out of time may invoke a test rule that looks at the last "x" number of questions answered. When I took the NCLEX-RN exam, the run out of time (ROOT) rule looked at the last 60 or 70 questions (assuming minimum questions have been answered) and if those showed "above passing standard" then you passed. If you got to the end of the questions, a similar process was followed. One thing to remember is that the exams should pretty quickly ramp up to above passing standard (go from moderately hard to very hard). If you're getting relatively easy questions, you're either well below passing or you're so well prepared that the majority of questions that will ever be presented are going to be easy.
These adaptive exams are usually pretty good at figuring out where the limits of your knowledge are and will ride that bleeding edge of what you know. Therefore, these are usually among the most difficult types of exams you'll ever take and because they are very hard, it's not uncommon (at all) to feel like you failed the exam. You can answer the last questions correctly and still be below passing standard. These exams aren't just about answering a question correctly or not, it's also about the level of difficulty the question poses.