Does prayer become invalid upon feeling something from the urine has fallen, even if there is no trace of it in most cases?

Mere doubt about the emission of an impurity (hadath (definition)) is not taken into consideration. Ablution (wudu') is not invalidated by it, and prayer (salat) is not nullified. Certainty is not removed by doubt. Therefore, whoever is certain of their purity and doubts the emission of an impurity, whether they are in prayer or outside of it, their ablution remains valid, and they should not exit their prayer unless they are certain of the impurity. Consequently, one must ignore these doubts and continue their prayer. If you become certain of something, then act according to what it dictates.