if he was in the Defence of Ladysmith, it is simply impossible for him to have been wounded at Colenso
. He would have been wounded in the besieged town at Ladysmith
, >20 km north of Colenso. The reason is that the siege was very tight, and no British troops were patrolling as far south as Colenso at any time during the siege. By 15th feb, when he was wounded, the garrison were too weak to do much at all, so he was probably wounded by a long-distance Mauser bullet, a shell fragment, or an accident.
So, how could news of the wound have come from Colenso, then? Well, prior to the siege being lifted (28 Feb) the Ladysmith garrison was in regular heliograph signal contact, searchlight signal contact, and "native runner" contact with the relieving force at Colenso, so it is quite possible the garrison reported his being WIA to Colenso, and the despatch would have then come to the outside world from Colenso.
Or his wound could have been reported from Colenso after the siege was lifted.
When in Ladysmith, he may have possibly have been treated at Intombi Military Hospital, which you can read about here: http://samilitaryhistory.org/vol056sw.html