Yes, 問う is a special verb. See the following explanation in Wikipedia.
Perfective Type of word: v5u-s -う -u (See Usage) Perfective: -うた -uta, -ota Examples: 問う tou (ask) Perfective:問うた tōta
Usage
Note that the perfective conjugation for verbs ending in -う more commonly follows the v5u-s pattern listed above for speakers of Western Japanese.