The lack of any official battle doesn't mean that there was no fighting. Artillery fire continued (though at a lower rate than in major battles), snipers were still shooting, and there were patrols and trench raids. As well as being on the receiving end of such things in the trenches, tasks such as repairing barbed wire in front of the positions would take soldiers out of the trenches exposing them to further danger. The British termed this steady trickle of losses "normal wastage" (with losses in general, including those from major battles, being "wastage").

The entire Western Front, in quiet times, was a "smaller battle".

The numbers I see given for "normal wastage" vary a lot, from 35,000 per month down to about 13,000 per month in quiet periods. Some of this variation presumably results from what is counted as "normal activity" and what is a "battle", and whether only wounded or dead are counted, or whether normal wastage includes disease, and whether men who returned to their units after recovery from illness or minor wounds are counted, etc. Normal wastage rates also varied along the front, and could be quite high in places.

In April 1918, Australian forces lost a minimum of over 30 dead per day, rising to highs of 415 and 323 deaths on the 5th and 24th respectively. This shows both the difference between casualty rates between quiet times and active fighting, and the still significant losses during the quiet times.

The Australian War Memorial provides an online search which can be used to find deaths on a particular day:

https://www.awm.gov.au/advanced-search/people?people_preferred_name=&people_service_number=&people_unit=&people_fate_date=1918-04-10&roll=Roll+of+Honour

Do you know which unit he was a member of?